Question

r^2+8r=48


First bring the 48 to the other side of the equation

r^2+8r-48=0

Now you can use the quadratic formula.

x=-b+-sqrt(b^2-(4ac))
¯¯¯¯¯¯¯2a¯¯¯¯¯¯¯¯¯

So...
a=1
b=8
c=-48

Now just plug the numbers into the quadratic equation and get your two answers.

The answers are: x=-12 and x=4

Feel free to ask if you need any more help. :-)