75:15/120: 15=5/8
26*5/25*13=26:13/13:13* 5:5/25:(5)=2*1/5=2/5
Y`=5cos^4(10x²)*(-sin(10x²))*(20x)=-100x*cos^4(10x²)*sin(10x²)
6 7/12-3 17/36=6-3 7/12-17/36=3+21/36-17/36=3 4/36=3 1/9
4 1/3:65/100=13/3*100/65=1/3*100/5=100/15=20/3=6 2/3
3 1/9*2,5=28/9*5/2=14/9*5/1=70/9=7 7/9
<span>7 7/9-6 2/3=7-6 7/9-2/3=1-7/9-6*9=1 1/9</span>
Х - девочек
60+х - мальчиков
60+х+х = 100%
55% 100%
------ --------
60+х 60+2х
перемножаем
55(60+2х)=100(60+х)
3300+110х=6000+100х
110х-100х=6000-3300
10х=2700
х=2700:10
х=270 девочек
270+60 = 330 мальчиков
270+330=600 всего учеников