Answer
$P = 18.75W$
Work Step by Step
first we calculate resistance of each bulb
$ R =\frac{V^2}{P} =\frac{120^2}{75} \Omega $
$R = 192 \Omega$
now when they are connected in series to $120V $ supply, potential difference across each bulb will be $60V$
Power dissipated will be same for both bulbs and will be equal to
$P =\frac{ V^2}{R} = {(60)^2}{192} W$
$P = 18.75W$
