We can solve simple algebras by reversing the mathematical symbols and shifting the number or unknown to the other side of the equation.
+ turns to -
x turns to ÷
(or vice versa)
So, first step to solve this,
shift +1 to the other side, turn it into -1.
3x = 3 - 1
3x = 2
Now, shift x3 to the other side, turn it into ÷3.
x = 2 ÷ 3
x = 2/3 (or 0.6666666...)