we have
x+y+10=0 --------> equation A
x^2+y-2=0 ------> equation B
Isolate the variable y in equation A and equation B
so
y=-10-x
y=2-x^2
equate both equations
-10-x=2-x^2
solve for x
x^2-x=2+10
x^2-x-12=0
Solve with the formula of quadratic equation
a=1
b=-1
c=-12
therefore
the values of x are
x=4 and x=-3