You could also think of what the midpoint really is,instead of memorizing formulas. What you are doing is finding the average of the x and y values.
Actually, these two equations represent the same line, and therefore has an infinite number of solutions. For example, if x=0, y=¾, If y=0, x=3. Therefore, two solutions are (0, ¾), and (2, 0).
Any number you chose for x, has exactly one value for y.
You can just divide the denominator into the numerator. eg. 3/4 = .75.