i dont understand how to answer the problem. can you please help. i really appreciate it thanks.

how much energy does it take to convert 0.500 kg ice at -20°C to steam at 250°C? specific heat capacities: ice, 2.03 j/g•°C; liquid, 4.2 j/g•°C; steam, 2.0 j/g•°C, ΔHvap= 40.7 kj/mol, ΔHfus= 6.02 kj/mol.

you have got to have a feel for what is going on here, draw a cycle(so called hess cycle)

H2O(s) at 253 K ---> H2O(s) at 273 K ---> H2O(l) at 273 K ---> H2O(l) at 373 K ----> H2O(g) at 373 K ---> H2O(g) at 523 K

use specific heat capacity for transitions involving change in temperature
use the enthalpy of fusion/vaporisation to determine enthalpy change for transition

fusion = melting

surely you know the formula; if you don't look back in lesson notes, etc.