Hey there! :)
5x + 10 + 7x = -3 + 13 + 7x + 12
Add like terms.
(5x + 7x) + 10 = (-3 + 13 + 12) + 7x
Simplify.
12x + 10 = 22 + 7x
Now, we have to isolate x. To do that, we must start out by subtracting 10 from both sides.
12x = 22 + 7x - 10
Then, subtract 7x from both sides.
12x - 7x = 22 - 10
Simplify.
5x = 12
Divide both sides by 5.
x = 12/5 OR as a decimal, x = 2.4
~Hope I helped!~