Solve following system. 7x-y=10 and second equation is y=-7x+2.

Okay so let's first try to get the first equation in the same form as the second with y on one side.

We have 7x-y=10 so we will subtract 7x from both sides and we now have :

-y=-7x+10

Now we can add both equations!

   -y=-7x+10
+ y=-7x+2

We end up with 0=-14x+12

subtract 12 from both sides and we have -12=-14x

divide by -14 and we have 12/14=x  we can simply that fraction to 6/7.

Now that we know x=6/7, we can plug it into the equations to find y!

7(6/7)-y=10

7(6/7)=6  so we now have 6-y=10

Subtract 6 and we now have -y=4.  We want to also divide the negative sign since there's also an invisible one attached to it so the answer is y=-4

Let's plug in 6/7 into the second one to see if we get -4 too! 

y=-7(6/7)+2

y=-6+2

y=-4

So there we have it! x=6/7 and y= -4!  Sorry i took so long!