What are the degrees of freedom for a t-test with 12 subjects measured on both the pretest and posttest

Plot the points (0,6), (3,15.8), and (9.5,0) using the graphing tool, and find the function

Aiden buys two bags of chips at $1.09 each and a 20 ounce soda for $1.20 at the gas station. he knows that the state tax is 5.5. how much change will he receive from a $5 bill?

Which expression gives you the distance between the points (5,1)and(9,-6)