3. 90:30 80:40 5.20-16 74-60:2 7.(42-34) (36+36):9 0.1:5 0:5:2

3.

• $$90:30 = 3$$
  


• $$80:40 = 2$$
  


• $$5 \cdot 20 - 16 = 100 - 16 = 84$$
  


• $$74 - 60:2 = 74 - 30 = 44$$
  


• $$7 \cdot (42-34) = 7 \cdot 8 = 56$$
  


• $$(36 + 36) : 9 = 72 : 9 = 8$$
  


• $$0.1 : 5 = 0.02$$
  


• $$0.5 : 2 = 0.25$$
  

Ответ: 3; 2; 84; 44; 56; 8; 0.02; 0.25.