I'll do the first one.
3x - y = 5
y = 4x + 2
y = 4x + 2
Substitute 4x+2 from the second equation for y in the first equation:
3x - y = 5
3x - (4x+2) = 5 [substituted 4x+2 on place of y]
3x - 4x - 2 = 5
-x - 2 = 5
-x = 7
x = -7
Now solve for y by putting x = -7 into one of the original equations:
y = 4x + 2
y = 4*(-7) + 2
y = -28 + 2
y = -26
Check by plugging x=-7, y=-26 into the original equations:
3x - y = 5
3*(-7) - (-26) = 5
-21 + 26 = 6
5 = 5 Check!
y = 4x+2
-26 = 4*(-7) + 2
-26 = -28 + 2
-26 = -26 Check!
------------
For the second problem
2x-y = 1
5x-5y = 10
Start by re-arranging the first equation to solve for y:
2x - y = 1
2x - 1 = y
Now substitute 2x-1 in place of y in the second equation (5x-5y=10) and solve for x. Then solve for y. Then check you work.
