To write the equation, you can start with the answer of $680. She receives $400 + $20*plans sold:
400 + 20p = 680
20p = 280
p = 14
{$400 + $20 * 14 = 680}
Sam sold 14 plans to make a total of $680.
Given:
sales discount = 30%
sales tax = 12%
c(p) = 0.7p where p is the original price
f(c) = 1.12c where c is the sales price of the bike.
f[c(p)] = 1.12(0.7p)
f[c(p)] = 0.784p Last option.
Assume: p = 100
c(100) = 0.7(100) = 70
f(70) = 1.12(70) = 78.4
f[70(100)] = 0.784(100) = 78.4
-1/3b = 9
b = 9 * -3
b = -27
