<span> 1 - 90 </span>книг<span>, 2 - 30 </span>книг<span>. х + </span>3<span>х = 120 4х = 120 х = 120:4 = 30 - </span>вторая<span> </span>полка<span> </span>3<span> * 30 = 90 - </span>первая<span> </span>полка<span>.</span>
1) 3/10 2/5
3/10 4/10
2) 5/9 7/18
10/18 7/18
3) 9/14 6/7
9/14 12/14
4) 1/5 7/25
5/25 7/25
5) 1/2 1/3
3/6 2/6
6) 2/5 3/7
14/35 15/35
7) 2/11 1/3
6/33 11/33
8) 5/8 1/6
15/24 4/24
9) 5/12 3/8
10/24 9/24
1м=10дм
1дм=10см
значит
1м=10дм=100см
значит
6м=60дм=600см
1) 6 3/4 - 2,9 = 6 3/4 - 2 9/10 = 6 15/20 - 2 18/20 = 5 35/20 - 2 18/20 = 3 17/20
2) 3 17/20 * 4 = 77/20 * 4 = 77/5 = 15,4
3) 7 5/8 - 3,25 = 7 5/8 - 3 1/4 = 7 5/8 - 3 2/8 = 4 3/8
4) 4 3/8 : 7/8 = 35/8 * 8/7 = 5
5) 15,4 + 5 = 20,4
50*30=15*у
1500=15*у
у=1500:15
у=100
проверка:
(50*30)/100=15
1500/100=15
15=15
ответ: у=100