If $y = 2x$ and $z = 2y$, then $x + y + z$ equals 
$\text{(A)}\ x \qquad  \text{(B)}\ 3x \qquad  \text{(C)}\ 5x \qquad  \text{(D)}\ 7x \qquad  \text{(E)}\ 9x$
Solution by e_power_pi_times_i
$x+y+z = x+(2x)+(4x) = \boxed{\text{(D)}\ 7x}$