halps

Well, think about it! A slope of seven means that the $\frac{\text{change in y}}{\text{change in x}}=7$. So, using our formula, we can make an equation from your points, giving$\frac{2a-(-2)}{6-a}=\frac{2a+2}{6-a}=7$. See if you can solve the equation for yourself now!