-238 + 742 = 504
504 - 42 = 462
-356 + 145 = -211
-211 - 56 = -267
-79 - 39 + 81 = -117
-117 + 81 = -36
Therefore, the final answer is -36.
-238 + 742 = 504
504 - 42 = 462
-356 + 145 = -211
-211 - 56 = -267
-79 - 39 + 81 = -117
-117 + 81 = -36
Therefore, the final answer is -36.