To solve this question, we need to know a particular law of logarithm. This law is stated below:
[tex]\log _ab+\log _ac=\log _a(b\times c)[/tex]
From the question, it is obvious that:
a = 7
b = 20
x = c
Therefore, we can re-write the question as:
[tex]\begin{gathered} \log _720+\log _7x=\log _a(20\times x) \\ \\ \therefore\log _a(20x) \end{gathered}[/tex]
