1) 5/x = y / 20 → 5= x × y / 20 → x×y =100
2) 250 км = 25000000см
5см/25000000см = 1/5000000
3) -7; -6; -5; -4; -3; = 5
5) А= 2; В=8; |2-8|=|A-B|
6) 50→100% x→40% x→30
30→ 100 y → 20 y = 6
(50- 30)-6=24
8) -1/20-1.05+0.1= -1