Answer
$log_b{(x^5y^6)}$
Work Step by Step
The product rule for logarithms says that $log_b{MN}=log_bM+log_bN$ i.e. the logarithm of a product is the sum of the logarithms.
The quotient rule for logarithms says that $log_b{\frac{M}{N}}=log_bM-log_bN$ i.e. the logarithm of a quotient is the difference of the logarithms.
The power rule for logarithms says that $\log_b{M^p}=p\log_bM$ i.e. the logarithm of a number with an exponent is the exponent times the logarithm of the number.
$\log_ba=\frac{\log_ca}{\log_cb}$
Hence here: $5\log_bx+6\log_by=\log_b{x^5}+\log_b{y^6}=log_b{(x^5y^6)}$