Question

20 x+3(y-1)=11
2(x-y)+8y = 28

multiply out
20 x+3y-3=11 - Is this correct?

2x+14y = 28

Using the addition method, would you multiply the first problem by 2 and the second by 20?

No. In the second multiply out, you should have gotten

2x -1y+8y=28 or
2x+7y=28

No, in the addition method
20x+3y=14
2x+14y=28
multiply the second equation by ten, then subtract one from the other.


Bob, I read the questions as
x+3(y-1)=11 ------> x+3y = 14 and
2(x-y)+8y = 28----> 2x-2y+8y=28 or x+3y=14

which are two identical equations.
I think the 20 was the question number.