Explain why you set an absolute value equal to a positive number and equal to a negative number to solve?

Can someone me with #s 8, 9, and 11. with just one of the three also works. prove using only trig identities.

The dimension of the rectangular pool shown below are 40 yards by 20 yards

Travis has decided to budget his spending money. he can spend no more than $143.15 every month. he has also decided to spend 5.2 times as much money on video games as he spends on the movies.what linear inequality describes this problem