To find the price of the kayak at the end of four months, start with the initial price and subtract the total amount reduced over the four months.
- Initial price of the kayak: $378
- Monthly price reduction: $15
- Total reduction over four months: \(15 \times 4 = 60\)
Now, subtract the total reduction from the initial price:
\[ 378 - 60 = 318 \]
The price of the kayak at the end of four months is $318.