The freshmen competed with the sophomores to see who could raise the most money by recycling. The appropriate design for testing the significance of the difference between the means is

Independent-samples t-test.

Step-by-step explanation:

We are looking for the appropriate design for testing the significance of the difference between the means.

Now, there is a parametric test known as the Independent Samples t Test and what this test does is that it compares the mean of two independent groups in order to find out whether there is statistical evidence that the related population mean is significantly different.

Thus, the test to be used here is Independent-samples t-test.

x=-7

step-by-step explanation:

x+3=-10

-10+3=-7

x=-7