For what values of the variables are the following expressions defined? 1/x+7

An expression f(x) is undefined when we have a zero in the denominator,

if our expression is

f(x) = 1/(x +7)

then the denominator is x + 7, and this is only zero when x = -7.

Then, we have that our expression is defined for all the real values except x = -7

we can write this set as:

D = {x ∈ R ∧ x ≠ -7}

(which says "x is a real number and x is different than negative seven")

the solution is h=10 because you add 9 to each side of the equation.