Solve g=3h-j/j for h

Look at the operations performed on h. They are (in order) ...

multiply by 3 subtract j divide the difference by j

To solve for h, we undo these operations in the reverse order.

multiply by j: gj = 3h - j add j: gj+j = 3h divide by 3: (gj + j) / 3 = h

The desired equation is ...

... h = (g·j + j) / 3