Answer
$\dfrac{2}{3}$
Work Step by Step
Consider $V=\int_{0}^{2} \int_{0}^{y}
int_0^{(2-y/2)} dz \space dx \space dy$
or, $=\int_{0}^{2} \int_{0}^{y} (1-\dfrac{y}{2}) dx dy$
or, $=\int_0^2 (y-\dfrac{y^2}{2}) dy$
or, $Volume =\dfrac{2}{3}$