# How do you solve 2/5 + 7/8 = y/20 ?

May 30, 2015

Multiply through by $20$ to find:

$y = 20 \cdot \frac{y}{20} = 20 \cdot \left(\frac{2}{5} + \frac{7}{8}\right)$

$= \left(20 \cdot \frac{2}{5}\right) + \left(20 \cdot \frac{7}{8}\right)$

$= \frac{\cancel{5} \cdot 4 \cdot 2}{\cancel{5}} + \frac{\cancel{4} \cdot 5 \cdot 7}{\cancel{4} \cdot 2}$

$= 8 + \frac{35}{2}$

$= \frac{16}{2} + \frac{35}{2}$

$= \frac{51}{2}$