I need help understanding how to get the answer.

Answer:
-157.87
Step-by-step explanation:
1) the rules are:
[tex]log_a(bc)=log_ab+log_ac;[/tex]
and
[tex]log_ab^c=c*log_ab.[/tex]
2) according to the rules above:
[tex]log_7(yz^8)=log_7y+8log_7z=-6.19-8*18.96=-157.87.[/tex]