x/y = 4/9
a) y = 9x/4 = 2,25x (3x+2y)/(5x +y) = (3x +5,5x)/(5x + 2,25x) = 8,5x/7,25x =
= 17/14,5 = 170/145 = 34/29
b) x/y = 3/5 (x+y)/y = 8/5 x+y = 8y/5 = 1,6y x = 0,6y
(4x +6y)/(x +y) = (2,4y + 6y)/1,6y = 8,4y/1,6y = 5,25
c) x/4 = y/7 y = 7x/4 = 1,75x
(9x-2y)/(x +3y) = (9x - 3,5x)/(x+5,25x) = 5,5x/6,25x = 0,88
d) x/2 = y/9 y = 9x/2 = 4,5x
(10x - 2y)/(5x+y) = (10x - 9x)/(5x+ 4,5x) = x/9,5x = 1/9,5 = 10/95 = 2/19