Question 604526
(4 x 9 ÷ ?) ÷ (4 x 5) x 5 = 1.8
(36 ÷ ?) ÷ 20 x 5 = 1.8
(36 ÷ ?) ÷ 20 = 1.8 ÷ 5
(36 ÷ ?) ÷ 20 = 0.36
(36 ÷ ?) = 0.36 x 20
36 ÷ ? = 7.2
? = 36 ÷ 7.2 = 5