If x + 2y = 10 and 3x − y = 9, what is the value of x − y?
A1
B2
C3
D4
E5
Explanation
From x + 2y = 10, we get x = 10 − 2y. Substitute into 3x − y = 9: 3(10 − 2y) − y = 9, so 30 − 7y = 9, giving y = 3. Then x = 10 − 6 = 4, and x − y = 4 − 3 = 1.
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