-3 (4x + 3) + 4(6x + 1) = 43.
-12x + -9 + 24x + 4 = 43.
Combine like terms:
-12x + 24x = 43 + 9 - 4.
12x = 48.
Divide both sides by 12:
12x / 12 = 48 / 12.
x = 4.