Răspuns :
(20:a+20):6=5
(20 : 2 + 20 ):6 =5
(10 + 20) : 6=5
30 : 6 = 5
adica
20:a+20=30
20:a = 30 -20
20: a = 10
a = 20 : 10
a = 2
(20 : 2 + 20 ):6 =5
(10 + 20) : 6=5
30 : 6 = 5
adica
20:a+20=30
20:a = 30 -20
20: a = 10
a = 20 : 10
a = 2