Answer
$5$ consecutive hits
Work Step by Step
$\displaystyle \frac{30+x}{120+x}=0.28\qquad$ ... $0.28=\displaystyle \frac{28}{100}=\frac{7}{25}$
$\displaystyle \frac{30+x}{120+x}=\frac{7}{25}\qquad $... $/\times 25(120+x)$
$25(30+x)=7(120+x)$
$ 750+25x=840+7x\qquad$ ... add $-750-7x$
$18x=90$
$x=5$
