Hey There!:
Total number of moles of gases:
0.150 + 0.419 + 0.211 => 0.780 moles
Volume = 0.250 L
Temperature = 298 K
Using the ideal gas law:
p*V = n*R*T , putting all the values we get :
p * 0.250 = 0.780 * 0.0821* 298
p* 0.250 = 19.083
p = 19.083 / 0.250
p = 76.3 atm
Hope That helps!