Question

r+35=81       71+r =90        41-r =15

Answer 1

r+35=81
r=81-35
r=46
 v: 46+35=81

71+r=90
r=90-71
r+19
v: 71+19=90

41-r=15
r=41-15
r=26
v: 41-26=15