1) 19 - 15 4/7 = 3 3/7
2) 3 3/7 ÷ 16/21 = 24/7 <span>÷ 16/21 = 24/7 * 21/16 = 9/2 = 4 1/2
3) 4 1/2 + 6 3/5 = 4 5/10 + 6 6/10 = 11 1/10
4) 11 1/10 - 4 5/6 = 11 3/30 - 4 25/30 = 6 8/30 = 6 4/15</span>
15 вторых или 7 целых 1\2
300-100=200,66+834=900,525+177=702. наверно так :-))
Y*2.5=100
y=100:2.5
y=40
40*2.5=100
a:6=18
a=18*6
a=108
108:6=18