5x÷5 = 15/ 19÷5 8/2 1x÷8/2 1 = 4/ 15÷8/2 1x÷4/5×4/5 = 15/28×4/5

x=3/ 19 x=7/ 10 x=3/7

2/3÷ 1/4 = 12

2/3x÷ 1/4× 1/4 = 12× 1/4

2/3x=3

2/3÷2/3 = 3÷2/3

x =9/2

7.6 ÷ 3/50 = 100 (hours)

8.3 minutes = 180 seconds 180 ÷ 9/ 100 = 2000 (Zhang)

9. 12 ÷ (1/2× 3) = 8 (days) or 12 ÷ 1/2 ÷ 3 = 8 (days).