How do you subtract left-to-right, e.g. 764 − 328?

Take each place value in turn, biggest first, and adjust the running total when a column goes negative.

764 − 328 → hundreds: 700 − 300 = 400 → tens: 60 − 20 = 40, total 440 → units: 4 − 8 = −4, total 436.

Check: 764 − 328 = 436. ✓ Where a column would need a "borrow" (units: 4 − 8), you just let the running total absorb it (440 − 4 = 436). One running number, read out in order.