Answer: 22x
Step-by-step explanation: +7x and +15x are called terms and the numbers in front of the variables, +7 and +15 are called coefficients.
Because the variables, x and x, are identical, the two terms in this problem are called like terms. Like terms can be added together by simply adding their coefficients. So in this problem, since 7 + 15 is 22, 7x + 15x is simply 22x.