The Distributive law is used here. Can you expand the brackets?
Firstly , expand all the brackets.
This can be done by multiplying 2(the factor) into the bracket.
(nothing changes on the right side)
Now, 'move' the x to the left side and the 8 to the right side.
Subtract 8 and 4x from both sides.
Solve the other problems in the similar fashion. Hope this helps.