A) how many hydrogen atoms are in an acyclic alkane with 15 carbon atoms?

Alkanes belongs to saturated Hydrocarbons in which all carbon atoms are singly bonded to each other. As the term "Acyclic" is mentioned in statement, which means the absence of ring or cycles. Hence, the general formula for Saturated, Acyclic hydrocarbons (Acyclic Alkane) is;

                                                 CnH₂n₊₂

As,
                                               n  =  15
So,
                                              C₁₅H₂₍₁₅₎₊₂

                                              C₁₅H₃₀₊₂

                                              C₁₅H₃₂
Result:
          There are 32 Hydrogen atoms in an Acyclic Alkane with 15 Carbon Atoms.

The third choice .. (:

m=9

step-by-step explanation:

7m+8=71 subtract   8 from 71 which is 63 than divide it by 7m   equal 9.