1. a/b = c/d b = ad/c
(5a + 2b)/(13a + 7b) = (5a +2ad/c) /(13a + 7ad/c) = (5 +2d/c) /(13 + 7d/c) =
= (5c + 2d)/c · c/(13c + 7d) = (5c +2d)/13c + 7d)
2. (x - y)/2 =( y + z)/8 = (x +z)/10 = z/6
(x+z)/5 = z/3 3x + 3z = 5z 3x - 2z = 0
x +2z = 48
4x = 48 x = 12 z = 36/2 = 18 (12-y) /2 = 18/6 12 - y = 6 y = 6