x/y = 7/9 => x/7 = y/9 = z =>
x = 7z si y = 9z
Înlocuim x si y in relatiile de mai jos:
a) (5x+2y)/(2x-y) = (5×7z+2×9z)/(2×7z-9z) = (35z+18z)/(14z-9z) = 53z/5z = 53/5
b) (x+8y)/(3x+6y) = (7z + 8×9z)/(3×7z + 6×9z) = (7z+72z)/(21z+54z) = 79z/75z = 79/75
