24 − 35.75 + 12.50
Sam has twenty-four dollars in his account. He pays a thirty-five dollar and seventy-five cent bill, then deposits twelve dollars and fifty cents. What's his balance?
We can write Sam's story as one expression: twenty-four minus thirty-five seventy-five plus twelve fifty.
Going left to right, we start with the first two numbers — twenty-four minus thirty-five seventy-five.
Sam is paying more than he has, so the answer must be negative.
Twenty-four minus thirty-five seventy-five is negative eleven dollars and seventy-five cents.
On the number line, that lands here — eleven seventy-five below zero.
Now we add the twelve-fifty deposit to negative eleven seventy-five.
Negative eleven seventy-five plus twelve fifty equals positive zero point seven five.
We jump up twelve and a half on the number line — across zero — and land at seventy-five cents.
Does this make sense? The deposit was just a bit bigger than the overdraft, so a small positive answer fits.
Sam's final balance is seventy-five cents. That's how we tackle multi-step problems with rational numbers!