Answer:
n = m-a
Explanation:
The formula is : ...(1)
a is actual cost of an item
m is original price
n is amount of coupon
We need to solve the formula for the amount of coupen.
Subtracting m to the both sides of equation (1).
a-m = m-n-m
-n=a-m
or
n = m-a
So, the formula for the amount of coupon is n = m-a.