C.
A doesn't work because x + x + x = 3x, not x^3.
B doesn't work because 14x + 10 - 2x has like terms, 14x and -2x can be combined, bit when you do so you get 14x - 2x, or 12x + 10. (So not 16x + 10)
D doesn't work because 12x^2 + 5x + 10 doesn't simplify; it can only be factored, and you cannot combine 12x^2 and 5x because their variables have different powers.
C, however, works fine. All they did is factor out a 3; if you distribute that 3 again, you get 12x + 16x back, so the two are equal.
Answer:
a. csc²θ
Step-by-step explanation:
You can use the identities ...
1 +tan² = sec²
cot = cos/sin
sec = 1/cos
csc = 1/sin
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Then the expression becomes ...

Answer:
31,41,51,71
Step-by-step explanation: