Answer:
12x - 5 = 10 - 34x
1. Change side of „x” to left side, without forgetting to change the sign, and numbers to right without forgetting to change the sign:
12x + 34x = 10 + 5
46x = 15
2. Simplify, by dividing both sides by 46 (num of x):

Proof:

, and if two sides are same, equation is correct.