se da: x/y=2/7
a)
2x/3y=2/3 · x/y = 2/3 · 2/7 = 2·2 / 3·7 = 4/21
b)
(x+y ) / y = x/y+y/y=2/7+1=9/7
c)
x / (y-x) = daca x/y=2/7 ⇒x=2y/7⇒inlocuim valoarea lui x in functie de y
(2y/7) / (y-2y/7) = 2y/(7y-2y) = 2y/5y = 2/5
d)
(2x+3y) / 5y = 2x/5y+3y/5y = (2x2) / (5x7) +3/5 = 4/35 +21/35 = 25/35=5/7