20x+5y=120
10x+7.5y=80 multiply this one by 2
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20x+5y=120
20x+15y=160 subtract
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-10y=-40 divide both sides by -10
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y=4
20x+5(4)=120 plug 4 in for y in the first equation
20x+20=120 multiply
20x=100 subtract
x=5 divide to find x
