I just ask this question on the SnapCalc app the answer is in the image
F(x) = 112 - kx
f(-3) = 121
f(-3) = 112 - k(-3)
f(-3) = 112 + 3k
121 = 112 + 3k
121 - 112 = 3k
9 = 3k
9/3 = k
3 = k <===
Answer:
$40
Step-by-step explanation:
x is the original price of the gift
(10% of x) is the value of the discount
(10% of x) = 10/100 . x = 0.1 x
0.1 x is the value of the discount
x - (10% of x) is what was paid, after the discount
x - 0.1 x = 0.9 x
0.9 x is what was paid
4 children paid $9/each
4 times $9 = $36
$36 is the total amount that was paid by the children
$36 = 0.9 x
$36 / 0.9 = x
x = $36 / 0.9 = 360 / 9
x = 40
;-)
