Answer:
5
Explanation:
If we consider half the first purchase, it is
2 used + 1 new = $42
And the second purchase is
6 used + 1 new = $78
Subtracting the first of these equations from the second, we get ...
4 used = $(78 -42) = $36
used = $9 . . . . . . . . . . . . . . divide by 4
Then we can find the price of a new game from ...
new = $42 - 2 used = $42 -2·9 = $24
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The number of used games Janet can purchase on her budget is ...
($120 -3·$24)/$9 = $48/$9 = 5 1/3 ≈ 5
Janet can purchase 5 used and 3 new video games for $120. (and have $3 left)