Hello Detori
To solve your problem you must use inverse operations. But also try and keep all the variables to a side, and keep the numerals to a side.
x-7-7x = -5x-12
x-7 = -5x-12+7x
x-7 = 2x-12+7
x = 2x-29
2x-x=29
x = 29
I hope this helps, Eight-cord