Art book (#2)

Some math questions coz im bored

I've already solved them
Can you solve them??
5x - 3 = 12 - 2x
12 • (x - 1) + 9 = 36 + 2x
μ • (x + 6) - 2 = (2μ - 1) x + 2
3x - 1 + 8 - 2(-x - 1) = 1

If you're interested go ahead
If you're not then don't do them