Răspuns :
x+y=56
x/y=3/5
x+y=56
5x=3y
x+y=56
5x-3y=0
x=56-y
5(56-y)-3y=0
x=56-y
280-5y-3y=0
x=56-y
8y=280
x=56-y
y=280/8
x=56-y
y=35
x=56-35
y=35
x=21
y=35.
Verificare:
35+21=56;
Bafta!
a+b = 56 si a/b=3/5 ⇔ a/3 = b/5 = k ⇒ a=3k si b=5k
↑
3k + 5k = 56 => k = 7
⇒ a = 21 si b = 35