There are a various of ways solve this expression. We can choose to do completing the square method or to use the quadratic formula. In this case, I will choose to do completing the square. We do as follows:
x^2 - 7x = -13
x^2 - 7x + 49/2= -13 + 49/2
(x - 7/2)^2= 23/2
√[(x - 7/2)^2]= √(23/2)
x-7/2 = √46 / 2
x = √46 / 2 + 7/2
Hope this answers the question. Have a nice day.