If two fractions have the same denominators, then just simply add up the numerators together and keep the denominator.
Examples:

Let the original number be x
X^2 + 11 = 36
Subtract 11
X^2 = 25
Square root both
X = 5
Solution: her original number is 5
First of all, you can move the +2x to the other side:
-11 = -26 - 2x
Then you can move the -26 to the other side and then simplify:
-11+26 = -2x
15 = -2x
Then you can divide both sides by 2:
7.5 = -x
Then you can flip the sides and the signs around:
x = -7.5
No, The answer is not -7, it is -7.5
Hope this helps! :)