Răspuns:
30 : a × 8 = 40
30 : a = 40 : 8
30 : a = 5
a = 30 : 5
a = 6
25 × 4 : a = 10
100 : a = 10
a = 100 : 10
a = 10
27 : 3 × a = 81
9 × a = 81
a = 81 : 9
a = 9
5 × a : 2 = 10
5 × a = 10 × 2
5 × a = 20
a = 20 : 5
a = 4
a × 8 : 6 = 4
a × 8 = 4 × 6
a × 8 = 24
a = 24 : 8
a = 3
a : 7 × 5 = 15
a : 7 = 15 : 5
a : 7 = 3
a = 3 × 7
a = 21