Answer
12 atm
Work Step by Step
$P_{1}$ = 10. atm
$T_{1}$ = (25+273) K = 298 K
$T_{2}$ = (75+273) K = 348 K
According to Gay Lussac's law,
$\frac{P_{1}}{T_{1}}=\frac{P_{2}}{T_{2}}$
Or $P_{2}$ = $\frac{P_{1}T_{2}}{T_{1}} = \frac{10.atm\times348K}{298K}\approx$ 12 atm