Find the number that is the least common denominator of 4 and 10 by filling in the missing number.

$\displaystyle\frac{{3}}{{4}}=\frac{{15}}{?}\usepackage{cmbright}\Huge\$

$\displaystyle\frac{{7}}{{10}}=\frac{{14}}{?}\usepackage{cmbright}\Huge\$