How to solve in substitution

Y=2x-10

2y=x-8

2*y = x - 8, y = 2x - 10

2 * (2x-10) = x - 8

2*2x - 2*10 = x - 8

4x - 20 = x - 8 | + 20

4x = x + 20 - 8 = x + 12 | - x

4x - x = 12

3x = 12

x = 12:3

x = 4

y = 2*4 - 10

y = 8 - 10

y = - 2

2 (2x-10) = x-8

4x-20=x-8

3x=12

x=4