\[\frac{3y + 7}{4 - y} + \frac{y + 15}{y - 4} =\]
\[= \frac{3y + 7}{4 - y} - \frac{y + 15}{4 - y} =\]
\[= \frac{3y + 7 - y - 15}{4 - y} = \frac{2y - 8}{4 - y} =\]