x/0,3 = 10y/4 x = 0,75y
y/4 = 3z/5 z = 5y/12
a) 3y/4 + y + 5y/4 = 72 3y = 72 y = 24 x = 18 z = 10
b) 3y/4 - 5y/12 = 72 y/3 = 72 y = 216 x = 162 z = 90
c) y + 5y/4 = 90 9y = 360 y = 40 x = 30 z = 50/3
d) 9y²/16 + y² = 225 25y² /16 = 225 y²/16 = 9 y = 12 x = 9 z = 5
2. b = c - 15 b/c = 8/13
(c - 15)/c = 8/13 13c - 195 = 8c 5c = 195 c = 39 b = 24
a = 24/4 = 6 c/a = 39/6 = 13/2