вычислить рациональным способом:(2/3+3/4+4/5)+(1/6+2/7+3/8)+(5/8+5/7+5/6)+(1/5+1/4+1/3)

(2/3+3/4+4/5)+(1/6+2/7+3/8)+(5/8+5/7+5/6)+(1/5+1/4+1/3) =

2/3+3/4+4/5+1/6+2/7+3/8+5/8+5/7+5/6+1/5+1/4+1/3 =

(2/3+1/3) + (3/4+1/4) + (4/5+1/5) + (1/6+5/6) + (2/7+5/7) + (3/8+5/8) =

1 + 1 + 1 + 1 + 1 + 1 = 6;