Final answer:
To find the fraction of cabins with windows, divide the number of cabins with windows (21) by the total number of cabins (80), resulting in the fraction 21/80, which is in its simplest form.
Step-by-step explanation:
To determine what fraction of the cabins have windows, we need to look at the number of cabins with windows compared to the total number of cabins. There are 80 cabins in total on the ship, and 21 of these cabins have windows. The fraction of cabins that have windows can be represented as the number of cabins with windows over the total number of cabins, which is 21/80.
This fraction can be simplified if there are any common factors between the numerator (21) and the denominator (80). However, since 21 and 80 do not have any common factors other than 1, the fraction 21/80 is in its simplest form. Therefore, 21/80 of the cabins on the ship have windows.