Help please I don’t understand it

15) 30

16) 2

for 15 you plug the -4 into the variable (x)

so...

-4(-4)-4-2-5(-4)

you do multiplication first because of PEMDAS

so -4×-4=16 it is not negative because there 2 negatives so they cancel out

then -5×-4=20

then you get this:

16-4-2+20 which equals 30

then with 16 you do the same. you just put the number for y in the variable y and same with x

The correct  answer is about 1206.37

Step-by-step explanation:

V= π · r ^2 · h

V= π · 4^2 · 24

V≈ 1206.37