Answer: 6 large frames and 12 small frames
Explanation:
We define the following:
x = number of large frames
y = number of small frames
Make the following equations:
x + y = 18
19x + 9y = 222
Use system of equations to solve. We find the value of x first.
y = 18 - x
⇒ 19x + 9(18 - x) = 222
⇒ 19x + 162 - 9x = 222
⇒ 10x + 162 = 222
⇒ 10x = 60
⇒ x = 6
Find value of y:
6 + y = 18
y = 12
∴ 6 large frames and 12 small frames were purchased.