Question

Ernie went to the store and bought 33 apples. He bought three times as many red apples as he bought green, and he bought one-half as many yellow as he did red. How many of each type of apple did he buy?

Answer 1

(r is red, g is green and y is yellow)
r+g+y=33
r=3g
2y=r

substitution:
y=33-g-r
y=33-(1/3)2y+2y
y=33-8/3y
11/3y=33
y=33÷(11/3)
y=9

Solve for red and green:

r=2y
r=2×9
r=18

3g=r
3g=18
g=18/3
g=6

double check:
6+18+9=33

answer:
6 green apples, 9 yellow apples and 18 red apples.