Question

What is 6×5×4×7+z=9831

Answer 1

z=8711
6×5=30
30×4=160
160×7=1120
9831-1120=8711

Answer 2

6*5*4*7+z=9831

We move all terms to the left:

6*5*4*7+z-(9831)=0

z-9831+6*5*4*7=0

We add all the numbers together, and all the variables

z-8991=0

We move all terms containing z to the left, all other terms to the right

z=8991