You must simply KNOW that #1*atm# pressure will support a column of mercury that is #760*mm# high; and thus #"Torr"-=1*mm*Hg# stands in for a pressure measurement. You must also know the relationship between #"degrees Kelvin"#, and #"degrees centigrade"#: #0# #""^@C-=+273.15*K#

#V=(nRT)/P=(0.1*molxx0.0821*(L*atm)/(K*mol)xx310*K)/((700*"Torr")/(760*"Torr"*atm^-1))#

#=??*L#. The question would have been better proposed had it been specified that #0.1*mol# quantity of gas had been enclosed in a piston at the given temperature and pressure.