Help me you dont have to do all of them but if you do pls i will give you the brainiest

This is simple you just need to think what minus or plus the variable in each equation (letter that represents an unknown number) equals what the equations do

No. 19 X= -8
No.20 R=10
No.21 X=0
No.22 B=7
No.23 V=-4
No.24 N=10
No.25 X=7
No.26 K=4
No.27 N=-4
No.28 X=-7