What is the problem? What are you asked to do with this?
Are these base 10 or base 7 logarithms? IOW is the expression base 10 logs
or base 7 logs
Please use language like:
"5 times the base 10 log of 7x ..." or "5 times the base 7 log of x ..." to make the problem clear.
Please re-post your question and make the answers to these questions clear.