The common difference is $x$. The next term of the sequence: $4x+4$.
Work Step by Step
We are given: $4, x + 4, 2x + 4, 3x + 4, ... $ To find the pattern of this sequence we have to find the difference between consecutive terms of the sequence. 2nd term and 1st term: $x+4 -4 =x$ 3rd term and 2nd term: $2x+4-(x+4)=x$ 4th term and 3rd term: $3x+4-(2x+4)=x$ The common difference is $x$. We use this pattern to get the next term of the sequence: $3x+4+x=4x+4$