The total number of alpha hydrogens in ethyl acetoacetate, $\mathrm{CH}{}_3\mathrm{COCH}{}_2\mathrm{COOC}{}_2\mathrm{H}{}_5$, is

The $\mathrm{CH}{}_3$ attached to the ketone carbonyl has 3 alpha hydrogens. The $\mathrm{CH}{}_2$ between the two carbonyl groups has 2. The ethyl group of the ester is on oxygen, so its hydrogens are not alpha. Total $=3+2=5$.