c = boxes of candy chris sold
s = boxes of candy sean sold
s =chris + 4
s =c+4
chris boxes + sean boxes = 22
c+s = 22
substitute s= c+4 into the above equation
c + (c+4) = 22
combine like terms
2c+4 = 22
subtract 4 from each side
2c+4-4 = 22-4
2c = 18
divide each side by 2
2c/2 = 18/2
c =9
s =c+4
substitute c=9 into s=c+4
s = 9+4
s=13
Answer:Chris sold 9 and Sean sold 13
