Idon't get how to solve for x with prathesis

Just remember that something outside the parentheses applies to everything inside.

Examples:

3 times (x + 2) . . . . . means . . . . . 3 times 'x'  plus  3 times 2

a (b + c) . . . . . means . . . . . ab  plus  ac

4 (w + x + y + 2) . . . means . . . 4w + 4x + 4y + 8

When somebody gives you an equation that has parentheses in it,
the first thing you're always supposed to do is get rid of them. 
With the examples I just gave you, you know how to do that now.