$39 per week

$32 per week

$6 per week

$7 per week

$$f\left(x\right)\ =\ 12x\ -\ 28$$

$$f\left(x\right)\ =\ \frac{1}{12}x+1$$

$$f\left(x\right)\ =\ 12x\ +\ 58$$

$$f\left(x\right)\ =\ \frac{1}{12}x+20$$

x = 3

x = 4

x = 5/7

x = 2