2x-5y=8. x-5y=-2 solve the system of equations

Using subtraction 

2x - 5y =8
x-5y = -2

2x -x -5y -(-5y)= 8 -(-2)
x+0y = 10
x=10

Using the value of x, plug it back into one of the original equations

x-5y =-2
(10)-5y = -2
-5y = -2-10
5y=12
y= 12/5

hence the solution is 
x=10
y= 12/5

(10, 12/5)

For your first one :
2x−5y=8
2x−5y+5y=8+5y
2x=5y+8
2x2=5y+82
x=52y+4

For your second one : 

x−5y=−2
x=5y−2
x=5y−2

Hoped I helped!