2/7х + 3/7х = 2 1/2
5/7х = 5/2
х = 5/2 : 5/7
х = 5/2 • 7/5 = 7/2 = 3.5
7 = 3+4, 2+5, 1+6;
10 = 5+5, 6+4, 3+7, 8+2, 1+9;
18 = 17+1 / 1+17;
24 = 23+1, 20+4, 21+3, 5+19, 8+16, 9+15, 18+6, 17+7, 14+10, 13+11, 12+12, 22+2.
<span>9*(560:у-5)=27
560:y-5=3
560:y=8
8y = 560
y=70</span>