The values are…

DHorxn = 2 mol (-393.5 kJ/mol) + 3 mol (-285.8 kJ/mol) - 1 mol (-277.7 kJ/mol) - 3 mol (0 kJ/mol) = -1,367 kJ

The sign of this answer is negative. Is this an exothermic or an endothermic reaction? J