Chapter 7 - Algebraic Fractions - 7.3 - Adding and Subtracting Algebraic Fractions - Problem Set 7.3 - Page 291: 39

$\frac{11y}{12}$

By inspection, we see that the LCM of the denominators is $12$. Therefore, we create a common denominator to obtain: $\frac{y}{6}+\frac{3y}{4}$ $=\frac{2(y)+3(3y)}{12}$ $=\frac{2y+9y}{12}$ $=\frac{11y}{12}$