Adam earns $3 for every car he washes.
He gets $2 bonus for every 4 cars he washes.

1. How much will Adam earn if he washes every 4 cars?   
2. If Adam wants to earn $20, how many cars must he wash? 
3. If Adam wants to earn $42, how many cars must he wash? 
4. If Adam wants to earn $45, how many cars must he wash? 

(a)
Amount that Adam will earn for washing every 4 cars
= 3 x 4 + 2
= $14

(b)
Number of sets of $14
= 20 ÷ 14
= 1 r 6

Number of cars in 1 set
= 1 x 4
= 4

Number of extra cars that he has to wash
= 6 ÷ 3
= 2

Total number of cars that Adam must wash
= 4 + 2
= 6

(c)
Number of sets of $14
= 42 ÷ 14
= 3 (Note that there is no remainder.)

Total number of cars that Adam must wash
= 3 x 4
= 12

(d)
If Adam wants to earn $45, how many cars must he wash?

Number of sets of $45
= 45 ÷ 14
= 3 r 3

Number of cars in 4 sets
= 3 x 4
= 12

Number of extra cars that he has to wash
= 3 ÷ 3
= 1

Total number of cars
= 12 + 1
= 13

Answer(s): (a) $14; (b) 6; (c) 12; (d) 13