Answer :
Charles' Law states: V1/T1=V2/T2.
So you have:
0.600L/303°K=0.900L/x°K
x°K=(0.900L)/(0.600L/303°K)
x°K=454.5°K
So you have:
0.600L/303°K=0.900L/x°K
x°K=(0.900L)/(0.600L/303°K)
x°K=454.5°K