Answer:
Therefore Jet Skis cost $50 for the rental and Kayaks cost $20.
Explanation:
Since they both rent the vehicles at the same price, "x" for jet skis and "y" for kayaks", we can create equations for each store and a system of equations for these, as shown below:
Watersports:
12*x + 9*y = 780
Fun Rentals:
7*x + 11*y = 570
System:

We can isolate "x" on the first equation:

And use it on the second:
![7*[(780 - 9*y)/(12)] + 11*y = 570\\5460 -63*y = 6840 - 132*y\\132*y - 63*y = 6840 - 5460\\69*y = 1380\\y = 20\\](https://img.qammunity.org/2021/formulas/mathematics/high-school/7gf05is6saawxtgqqofw17vwofeo1c0ksu.png)
We can now use this value to find "x":

Therefore Jet Skis cost $50 for the rental and Kayaks cost $20.