You can put this solution on YOUR website! (7 x + -35) + (8 x + 125) = 90
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The only POTENTIAL problem I see is the +-35. But if you use the +35 then:
15x+160=90
15x=90-165
15x=-75
x=-75/15
x=-5 also not an valid answer.
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15x+90=90
15x=90-90
15x=0
x=0 ans.