7 + 4x - 10x + 15 = 22 - 6x
You just need to sum terms of polynomial with the same stage of x and not to mix them out. Note that terms without x are actually terms with x^0 because x^0 = 1
Therefore we sum 7 and 15 = 22 and
we sum 4x and -10x = -6x
Answer is B)
