In algebraic terms this is:

The integer is 2.
Functions can only have 1 value of 'x'.
Option A is not a function because it has two -5's
Option B is not a function because it has two -2's.
Option C is a function.
Option D is not a function because it has two 6's.
Answer:
x = 4
Step-by-step explanation:
we know that 72 and (2x + 10) add up to 90
90-72 = 18
(2x + 10) = 18
2x = 8
x = 4