Answer: x = 4
Explanation:
To solve this problem, make use of the fact that you may add anything to an equation, as long as you do it to both sides.
Simply add 4x to both sides to get:
13 = 1 + 3x
Then simply add -1 to both sides to get:
12 = 3x
Then, divide both sides by 3 to get:
4 = x
Hope it helps :) and let me know if you want me to elaborate.