16/21х - 3/7х = 2.48 - 1.18
(16-9)/21х = 1.3
1/3х = 1.3
1.3*3х = 1
х = 1/3.9
х = 10/39
#54
б)
3/4 + 12/16=(12+12)/16=24/16=1 8/16=1 1/2
г)
4/15 + 2/5=(4+6)/15=10/15=2/3
е)
3/7 - 3/8=(24-21)/56=3/56
1) 6 2/3 - 4 2/3 = 2,
2) 15 7/9 + 10 3/9 = 25 10/9 = 26 1/9,
3) 26 1/9 - 2 = 24 1/9
Ответ: 24 1/9
(n:30*100-n):4<span>(n:30*100-n):4=((100n-30n)/30):4=70n/120=7n/12</span>