18. If you add x and x, what is the result?
A. 2x
B. -2x
C.x2
D.2x2
19.Find the value of the expression 9a + 3 if a=5.
A.32
B. 40
C. 48
D.45
20. What must be added to a to obtain 7a?
A.5a
В. 6а
C. 4a
D. 3a
21. Which of the following is equal to 28?
A. 256
B. 128
C. 16
D. 32
22. Which of the following is equal to 8°?
A. O
B. 1
C. 8
D. 1/8
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