How do you find the percent error of pacing? i can't figure out how to get 2.25%

The pacing error is computed the same way the odometer error is computed:

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A percent change from the original is always computed as

... ((new value) - (original value))/(original value) × 100%

If the "new value" is less than the original, the change percentage will be negative.

Here, you are comparing distances measured by an odometer and by pacing to the distance measured using a tape. The tape is the reference (original). The odometer registers a larger distance, so its error is positive. Pacing registers a shorter distance, so its error is negative. The absolute value bars used in your computation ensure that both results are reported as positive numbers (and that the order of subtraction doesn't matter).