Răspuns :
a x 10 x 20 : 40 = 5
a x 10 x 20 = 5 x 40
a x 10 x 20 = 200
a x 10 = 200 : 20
a x 10 = 10
a = 10 : 10
a = 1
a x 10 x 20 = 5 x 40
a x 10 x 20 = 200
a x 10 = 200 : 20
a x 10 = 10
a = 10 : 10
a = 1