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
