Correct. Use the quotient property: $\displaystyle{\log}_{{b}}\frac{{M}}{{N}}={\log}_{{b}}{M}-{\log}_{{b}}{N}\usepackage{cmbright}\Huge\$

$\displaystyle{\log}_{{{4}}}{\left(\frac{{y}}{{16}}\right)}={\log}_{{{4}}}{y}-{\log}_{{{4}}}{16}\usepackage{cmbright}\Huge\$

Now $\displaystyle{16}={{4}}^{{2}}\usepackage{cmbright}\Huge\$ , so $\displaystyle{\log}_{{4}}{16}={2}\usepackage{cmbright}\Huge\$ . The question mark represents the integer 2.