You can put this solution on YOUR website! Recall that the degree of a polynomial (possibly multivariable) is the largest sum of the powers of the variables' exponents. For example, has degree 3, while has degree 7.
Since the exponents of a polynomial must be nonnegative integers (by definition), it is impossible for four variables w,x,y,z to exist in the same term. However, a four-variable polynomial such as satisfies, as it has degree 3.