Question 252775
x+2y=128 multiply by -20 & add.
20x+35y=2280
-20x-40y=-2560
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-5y=-280
y=-280/-5
y=56 number of couples tickets sold.
20x+35*56=2280
20x+1960=2280
20x=2280-1960
20x=320
x=320/20
x=16 number of single tickets sold.
Proof:
16+2*56=128
16+112=128
128=128