to solve for an unknown number, keep isolating it till it is all alone. in this case, first eliminate 3b by subtract 3b on both side, so you have AX=2f-3b
next, you need to eliminate A. because A multiplies x in this case, to eliminate it, you divide both side by A. on the left side, A divide A is one, so you only have one x remaining on the left side, x is now alone.
both side divided by A: x=(2f-3b)/A
solved.
