4x+8=20

see http://web2.0calc.com/questions/4x-8-20_1

4x+8=20

4x=20 - 8

4x=12

x=3

-4x+2y=-30

This has infinite number of solution,

such as x=1, y=-13, x=2, y=-11, x=3, y=-9.......etc.