2. There are 15 goldfish more than guppies. Therefore, the correct answer is: C. 15.
4. The number of fourth-graders that were at school that day are 89 fourth-graders.
In order to write a system of linear equations to describe this situation, we would assign variables to the number of goldfish and guppies, and then translate the word problem into a linear equation as follows:
Let the variable x represent the number of goldfish.
Let the variable y represent the number of guppies.
Part 2.
Since there are 6 times as many goldfish as guppies and a total of 21 fish in the tank, a system of linear equations that models the situation can be written as follows;
x = 6y
x + y = 21
By solving the system of linear equations simultaneously, we have:
y + 6y = 21
7y = 21
y = 3 guppies.
x = 6y
x = 6(3)
x = 18 goldfish.
Difference = 18 - 3
Difference = 15 goldfish.
Part 4.
Since there are 104 students in the fourth grade and 15 fourth-graders were absent, the number of fourth-graders that were at school that day can be calculated by finding the dfference;
Number of fourth-graders = 104 - 15
Number of fourth-graders = 89 fourth-graders.