#### Answer

$\frac{43y}{20}$

#### Work Step by Step

By inspection, we see that the LCM of the denominators is $20$. Therefore, we create a common denominator to obtain:
$\frac{3y}{4}+\frac{7y}{5}$
$=\frac{5(3y)+4(7y)}{20}$
$=\frac{15y+28y}{20}$
$=\frac{43y}{20}$