1) 7 - 3(x + 1) = x - 3(x - 1) - 3x + 4 = - 2x + 3 - 3x + 4 - 4 = - 2x + 3 - 4 - 3x = - 2x - 1 - 3x + 2x = - 2x - 1 + 2x - x = - 1
<img src="https://tex.z-dn.net/?f=%5Cfrac%7B-x%7D%7B-1%7D%3D%5Cfrac%7B-1%7D%7B-1%7D" />
x = 1
2) 7x + 5 - 2 = 8 + 4 - 2
7x + 3 = 10
7x + 3 - 3 = 10 - 3
7x = 7
<img src="https://tex.z-dn.net/?f=%5Cfrac%7B7x%7D%7B7%7D%3D%5Cfrac%7B7%7D%7B7%7D" />
x = 1
3) 5 - (2x - 4) = 9 - (2 + 3x) - 2x + 9 = - 3x + 7 - 2x = - 3x - 2 - 2x + 3x = - 3x - 2 + 3x
x = - 2
4) (3x + 1) - (x + 3) = 3(x + 1)
<img src="https://tex.z-dn.net/?f=3x%2B1-%5Cleft%28x%2B3%5Cright%29%3D3%5Cleft%28x%2B1%5Cright%29" />
2x - 2 = 3x + 3
2x - 2 + 2 = 3x + 3 + 2
2x = 3x + 5
2x - 3x = 3x + 5 - 3x - x = 5
<img src="https://tex.z-dn.net/?f=%5Cfrac%7B-x%7D%7B-1%7D%3D%5Cfrac%7B5%7D%7B-1%7D" />
x = - 5.