Answer:
11. 
12. 
13. 
14. 
15. 
16. 
17. 
18. 
Step-by-step explanation:
In all of them you just subtract the bottom exponent from the top exponent.
1.x+16
2.x-8
3.12/x
these are the algebraic expressions
Circumference of a circle=diameter times pi
50.24=d(3.14)
d=16
radius is half of diameter so radius is 8
Area of a circle=pi(r^2)
(3.14)(8^2)=(3.14)(64)=200.96