Final answer:
Decreasing £3680 by 15% involves multiplying £3680 by 15% (0.15) to get the decrease amount of £552. Subtracting £552 from £3680 gives the decreased total of £3128.
Step-by-step explanation:
To decrease £3680 by 15%, you first need to calculate what 15% of £3680 is. To do this, multiply £3680 by 0.15 (which is the decimal equivalent of 15%).
£3680 × 0.15 = £552
Now subtract this value from the original amount to find the decreased value.
£3680 - £552 = £3128
Therefore, when you decrease £3680 by 15%, you get £3128.