2 м 50 см = 250 см
250 * 1 : 5 = 50 см ушло на платье
480÷6=80 км за 1 час
80×8=640 км за 8 часов
(7х - 24) : 12 + 26 = 31
<span>(7х - 24) : 12 = 31 - 26
(7х - 24) : 12 = 5
7x - 24 = 12 * 5
7x - 24 = 60
7x = 60 + 24
7x = 84
x = 84 :7
<span>x = 12
проверка </span></span>(7* 12 - 24) : 12 + 26 = (84 - 24) : 12 + 26 = 60: 12 +26 = 5 + 26 = 31... 31 = 31
Х²-15х+q=0
1/x1+1/x2=5/12
(x1+x2)/x1•x2=5/12
{x1+x2=15
{x1•x2=q
15/q=5/12
5q=15*12
q=3•12=36
x²-15x+36=0
x1=12;x2=3
(2 1/2*2 1/2)*8/15-5/9=5/2*5/2*8/15-5/9=25/4*8/15-5/9=10/3-5/9=30/9-5/9=25/9