LOL, you both got different anwsers
789*12345678910 = 9740740659990
9740740659990-192837465 = 9740547822525
9740547822525+1098765321 = 9741646587846
126-9741646587846 = -9741646587720
-9741646587720+345 = -9741646587375
-9741646587375 is final answer