If x, y, and z are positive integers and 3x = 4y = 7z, then the least possible value of x - y + z is Choose one.
A) 33	B) 40	C) 49	D) 19	E) 61

Rationale: x - y + z = - 3 x / 4 + x + 3 x / 7 = ( - 21 + 28 + 12 ) x / 28 = 19 x / 28 19 is not divisible by 28 ( it ' s a prime # ) , so for least value , x = 28 answer - d
Answer: D