Here is the equation:
[tex] \frac{3}{4}p - 2 = 7 [/tex]
Switch the equation around and it becomes:
[tex] 7 + 2 = \frac{3}{4} p \\ 7 + 2 = 9 \\ \\ \frac{3}{4}p = 9 [/tex]
The sign changes. At first you were subtracting, and now you're adding. Divide both sides by [tex] \frac{3}{4} [/tex] to leave the variable alone.
[tex] \frac{3}{4} p \div \frac{3}{4} = p \\ \\ 9 \div \frac{3}{4} = 12 [/tex]
That means p = 12
