To find out how much the overhead expenses are, we can use the formula:

Overhead expenses = (Overhead percentage / 100) * Cost price

In this case, the overhead percentage is 12% and the cost price is 150, so the overhead expenses are:

Overhead expenses = (12 / 100) * 150

This simplifies to:

Overhead expenses = 0.12 * 150

So the overhead expenses are 18.

Total C.P IS Rs.168

To find out the selling price that would result in a profit of 10%, we can use the formula for profit:

Selling price = Cost price + Profit

In this case, the cost price is 168 and the profit is 10%, so the selling price is:

Selling price = 168 + (10/100) * 168

This simplifies to:

Selling price = 168 + 16.8

So the selling price is 184.8

However, we also need to account for the overhead expenses of 18, so the selling price should be 183 to earn a profit of 10%. 

C.P of 3 toffees = Re. 1; S.P of 3 toffees = 150% of Re.1=\frac{3}{2}
For Rs. 3/2, toffees sold = 3 for Re. 1, $toffeessold=(3\times \frac{3}{2})=2.$

To find out how much B paid A for the article, we can use the formula for profit:

Selling price = Cost + Profit

In this case, the selling price is 400 and the profit is 20%, so:

S.P FOR B = 400 + (20/100) * 400

This simplifies to:

S.P FOR B= 400 + 80

So B paid 400 +80 = 480 for the article.

To find out how much C pays B, we can use the same formula:

Selling price = Cost + Profit

In this case, the selling price is the amount that C pays, the cost is the 480 that B paid to A, and the profit is 10%. So:

Selling price = 480 + (10/100) * 480

This simplifies to:

Selling price = 480 + 48

So C pays 480 + 48= 528 to B. 

C.P of 200 kg of mixture = Rs. (80 x 13.50 + 120 x 16) = Rs. 3000
S.P. = 116% of Rs. 3000 ∴ \ = Rs. \left({116\over100}× 3000\right) = Rs.3480
∴ Rate of S.P of the mixture $$\therefore =Rs.\left(\frac{3480}{200}\right)=perkg=Rs.17.40perkg.$$

If an article is sold at a 200% profit, this means that the selling price is 300% of the cost price. The ratio of the cost price to the selling price can be expressed as a fraction, with the cost price as the numerator and the selling price as the denominator.

Since the selling price is 300% of the cost price, the fraction representing the ratio of the cost price to the selling price is 1/3.

So the ratio of the cost price to the selling price is 1/3.
 

Let C.P of each article be Re. 1 Then, C.P of 18 articles = Rs.18, S.P of 18 articles = Rs. 21.
$$\therefore Gain=(\frac{3}{18}\times 100)\mathrm{\%}=16\frac{2}{6}\mathrm{\%}$$

To find the percentage of profit, we can use the following formula:

Profit percentage = (Profit / Cost price) * 100

We can express the ratio of the cost price to the selling price as a fraction. Since the ratio is 10:11, the fraction representing the ratio is 10/11.

We can then use this fraction to find the profit and the cost price. The profit is the difference between the selling price and the cost price, so:

C.P = 10x

S.P = 11x

Profit = S.P - C.P

Profit = 11x - 10x = x

Profit percentage = ( x /10x )*100

Profit percentage = 10%

To find the gain percentage, you can use the following formula:

Gain percentage = (Gain / Cost) * 100

In this case, the cost is 100 - 15 = Rs.85 and the gain is 15, so the gain percentage is:

Gain percentage = (15 / 85) * 100

This simplifies to:

Gain percentage = 15/17* 20

So the gain percentage is 300/17%.