If Steven sold two boxes of candy less than Rodney and they sold 8 boxes, you can calculate how many boxes did each sell using the following steps:
Steven ... s = r - 2
Rodney ... r
s + r = 8
r - 2 + r = 8
2 * r = 8 + 2
2 * r = 10 /2
r = 5
s = r - 2 = 5 - 2 = 3
Result: Steven sold 3 boxes of candy and Rodney sold 5 boxes of candy.