Final answer:
To calculate the ratio of students with pets to those without, subtract the number with pets from the total number of students to find those without pets, resulting in a ratio of 18:30, which simplifies to 3:5.
Step-by-step explanation:
To find the ratio of the number of students who have a pet to the number of students who do not have a pet, we need to first determine how many students do not have a pet. Since 18 out of 48 students have a pet, then 48 - 18 = 30 students do not have a pet.
The ratio of students with pets to those without is therefore 18 to 30. This ratio can be simplified by dividing both numbers by their greatest common divisor, which is 6. So, 18 divided by 6 is 3, and 30 divided by 6 is 5, giving us a simplified ratio of 3:5.
Thus, the ratio of students who have a pet to students who do not have a pet is 3:5.