Răspuns :
a +b = 120
a -20 = b +20 = nr egale
a = 120 - b
120-b - 20 = b + 20
120 - b -20 - b = 20
2b = 20 - 20 -120
2b = 120
b = 120 : 2
b = 60
a + b = 120
a + 60 = 120
a = 120-60
a = 60
a -20 = b +20 = nr egale
a = 120 - b
120-b - 20 = b + 20
120 - b -20 - b = 20
2b = 20 - 20 -120
2b = 120
b = 120 : 2
b = 60
a + b = 120
a + 60 = 120
a = 120-60
a = 60