What is the missing number in the synthetic-division array?

The correct answer for this would be 7. The missing number in the synthetic division array is 7. So how did we get 7. Here is the step by step process.
-1 in the left most part is the coefficient of (x+1= 0) which makes it -1. Now, bring down 3, then multiply it by -1, and this given you -3 on the second row. -4 + -3 would be -7. Continue with the same step. -7 x -1 would be 7. And this is how we got the answer for the part with the question mark. Hope this answer helps.