# 94652, jackson   11.11.2014 18:23:47

94651,
A=x*21; x=A/21
A=y*28; y= A/28
A=(x+y)*t; t=A/(x+y)= 28*21/(28+21)=28*21/49=28*21/7*7=4*3=12

Copyright ©2011, Гостевая 29 Сектора