Answer :
$38 + $2(n) where n is the no. of cars.
Explanation:
He earns $38 daily which is fixed and additional $2 wage depends on the no. of cars which means no. of cars will determine how many $2's he earns.
25 cars = $38 + $2 (25) = $88
30 cars = $38 + $2 (30) = $98
35 cars = $38 + $2 (35) = $108
40 cars = $38 + $2 (40) = $118