Answer: -5
Reason:
We cannot divide by zero. This means the denominator cannot equal zero. If it was zero, then,
2x+10 = 0
2x = -10
x = -10/2
x = -5
Follow that chain in reverse to see that x = -5 causes the denominator 2x+10 to be zero. This is why we kick -5 out of the domain. Any other x value is valid.