Đáp án: a, Y=(22/105) b, Y=(28/15) c, y=(10/21)
Giải thích các bước giải:
a, (2/3) - Y - (1/5) = (2/5) - (1/7)
(2/3) - (1/5) - Y = (9/35)
(7/15) - Y = (9/35)
Y = (7/15) - (9/35)
Y = 22/105
b, (1/2) x y : (2/3) = 1/(2/5)
(1/2) x Y : (2/3) = (7/5)
(1/2) x Y = (7/5) x (2/3)
(1/2) x Y = 14/15
Y = (14/15) : (1/2)
Y = 28/15
c, (2/5) x Y + Y x (1/5) = 2/7
Y x (2/5 + 1/5) = 2/7
Y x (3/5) = 2/7
Y = (2/7) : (3/5)
Y = (2/7) x (5/3)
Y = 10/21
