Simplify: $715632 - 631104 - 9874 - 999$

### Concept & Logic When an expression contains one positive number and multiple negative numbers, it is mathematically safer and faster to sum all the negative numbers first, then subtract that combined total from the positive number. ### Step-by-Step Solution * **Calculation:** Group all the negative terms together: $$ -(631104 + 9874 + 999) $$ * Sum the grouped negative values: $$ 631104 + 9874 + 999 = 641977 $$ * Subtract this combined total from the initial positive number: $$ 715632 - 641977 = 73655 $$ ### Exam Strategy & Shortcut Use the "Last Two Digits" strategy to quickly eliminate options. The sum of the last two digits of the negatives is $04 + 74 + 99 = 177$ (so the total ends in $77$). Subtracting $77$ from the last two digits of the positive number ($32$ becomes $132$ after a borrow): $132 - 77 = 55$. The correct option must end in $55$. ### Common Pitfall Attempting sequential left-to-right subtraction (e.g., subtracting $631104$, then subtracting $9874$ from that result) vastly increases the chance of a minor arithmetic error and consumes significantly more time. ### Final Answer Therefore, the correct answer is **73655**.