The equation that represent a proportional relationship is:
![y=kx](https://img.qammunity.org/2023/formulas/mathematics/college/zfnjlk9kn7jg7cyy0nlnepmsiaxj3b2oge.png)
If cruise ship move 49.5 feet for every gallon that mean:
![\begin{gathered} y=kx \\ y=49.5x \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/istmlke2crupq5q98ynfvowxz6my0pryse.png)
Where y define a distance that cruise ships move and x fuel in gallon 49.5
is a proportionality constant.
Previousaly it moved 36 feet per gallon that mean:
![\begin{gathered} y=kx \\ y=36x \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/fke6vog6fshzj8oyu8adrn2lqjcgtesxuq.png)
Proportionality is 36 is define as value of y in unit value of x.