A store sold 30 sweatshirts. How many of each kind were sold?

Question

White one cost $9.95, and yellow ones cost $10.50. in all $310.60 worht of sweatshirts were sold

Answer 1

Let the number of white shirts be w, the number of yellow shirts be y:

1) w + y = 30  or  w = 30 - y

2) 9.95w + 10.50y = 310.60

substitute eq(1) into eq(2):

9.95(30 - y) + 10.50y = 310.60

298.5 - 9.95y + 10.50y = 310.60

combine like terms:

0.55y + 298.5 = 310.6

subtract 298.5 from both sides:

0.55y  = 12.1

divide both sides by 0.55:

y = 12.1/0.55 = 22 yellow shirts

using eq(1):

w = 30 - 22 = 8 white shirts

check using eq(2):

9.95(8) + 10.50(22) = 310.60

79.6 + 231 = 310.60

310.6 = 310.6

There were 8 white and 22 yellow shirts sold.