a) 2x + 4(x-1) = 2 + 4x
Multiply everything in the parenthesis by 4.
2x + 4x - 4 = 2 + 4x
Combine like terms.
6x - 4 = 2 + 4x
Subtract 4x from both sides.
2x - 4 = 2
Add 4 to both sides.
2x = 6
Divide 2 on both sides.
x = 3
b) 25 - x = 15 - (3x + 10)
Multiply everything in the parenthesis by -1.
25 - x = 15 - 3x - 10
Combine like terms.
25 - x = 5 - 3x
Add 3x to both sides.
25 + 2x = 5
Subtract 25 from both sides.
2x = -20
Divide 2 on both sides.
x = -10
c) 4x = 2x + 2x + 5(x - x)
Multiply everything in the parenthesis by 5.
4x = 2x + 2x + 5x - 5x
Combine like terms.
4x = 4x
This means that there is an infinite amount of solutions.
Hope this helps!