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Take a moment to practice subtracting when at least one negative number is involved. The expectation is that readers can make these calculations here without a calculator.

Subtract $-1$ from $9\text{.}$

Subtract $32-50\text{.}$

Subtract $108-(-108)\text{.}$

Find the difference $-5.9-(-3.1)\text{.}$

Find the difference $-12.04-17.2\text{.}$

Solution

After writing this as $9-(-1)\text{,}$ we can rewrite it as $9+1$ and get $10\text{.}$

Subtracting in the oppsite order with the larger number first, $50-32=18\text{.}$ But since we were asked to subtract the larger number from the smaller number, the answer is $-18\text{.}$

After writing this as $108-(-108)\text{,}$ we can rewrite it as $108+108$ and get $216\text{.}$

After writing this as $-5.9-(-3.1)\text{,}$ we can rewrite it as $-5.9+3.1\text{.}$ Now it is the sum of two numbers of opposite sign, so we can subtract $5.9-3.1$ to get $2.8\text{.}$ But we were adding numbers where the negative number was larger, so the final answer should be $-2.8\text{.}$

Since we are subtracting a positive number from a negative number, the result should be an even more negative number. We can add $12.04+17.2$ to get $29.24\text{,}$ but our final answer should be the opposite, $-29.24\text{.}$