Question

number 21 please and how to do it step by step

Answer 1

-4y+5x=8
3y-3x=-3  -->       divide by (3) y-x=-1
                 then multiply by (4) 4y-4x=-4

-4y+5x=8
4y-4x=-4    
---------------
x=4

then plug x=4 in
4y-4x=-4
4y-4(4)=-4
4y-16=-4
4y=12
y=3

solution: (4;3)