Answer:
4x
Explanation:
Like terms are terms that share the same variable (or base) and the same exponents.
5x and x are like terms in that they share the variable x but the coefficients are different.
To combine like terms you would look at the sign (in this case, a subtraction sign) and subtract the two coefficients.
There is an imaginary 1 in attached to x, so you are basically subtracting 1 from 5.
5x - x = 4x
4x is equivalent to 5x - x.