From the figure shown, triangle ABE is congruent to CDB,
It then follows that the proportion of the sides be related thus
[tex]\begin{gathered} \Delta ABE\cong\Delta CDB \\ \frac{AB}{CD}=\frac{BE}{DB}=\frac{AE}{CB} \end{gathered}[/tex][tex]\frac{y}{17}=\frac{x}{12}=\frac{42}{17}[/tex]
Combining the proportion with y and the known proportion to solve for
[tex]\begin{gathered} \frac{y}{17}=\frac{42}{7} \\ \frac{y}{17}=3 \\ y=3\times17 \\ y=51 \end{gathered}[/tex]
Hence, y=51
