According to the image given there is a right triangle formed in which we are missing one of the angles, for that we know that the sum of thr interior angles of every triangle has to be equal to 180°.
Using this information
[tex]90+48+Y=180[/tex]we clear the equation for Y
[tex]\begin{gathered} Y=180-90-48 \\ Y=42 \end{gathered}[/tex]The measure of angle Y is 42°.