№1. 28 × (2/7) = 4 × 2 = 8
120 × (7/10) = 12 × 7 = 84
45 × (2/9) = 5 × 2 = 10
1000 × (2/5) = 200 × 2 = 400
№2. 18 ÷ (2/5) = 18 × (5/2) = 9 × 5 = 45
27 ÷ (3/4) = 27 × (4/3) = 9 × 4 = 36
15 ÷ (5/6) = 15 × (6/5) = 3 × 6 = 18
16 ÷ (4/9) = 16 × (9/4) = 4 × 9 = 36