First solve for x or y for either equation. I generally solve for y, but it doesn't matter. rearranging equation one will be: y=3x-4 Then replace that equation for y in the second equation x+5(3x-4)=-4
Then rearrange to find x. x+15x-20=-4 16x-20=-4 16x=16 x=1
Do the same for problem 8. y is already solved for you in the second equation. so x+7x+4=4 8x+4=4 8x=0 x=0.
