If an angle is marked with a square, this angle is a right angle.
y=9
Practice makes perfect
We have been asked to find the value of y. The expression m∠ BDJ is the angle measure between the rays DB and DJ. Similarly, m∠ JDR is the angle measure between the rays DJ and DR.
Since ∠ RDB is marked with a square, it means that it is a right angle. Therefore, m∠ RDB = 90. Moreover, the sum of m∠ JDR and m∠ BDJ is equal to m∠ RDB.
m∠ JDR+ m∠ BDJ= m∠ RDB
Let's substitute 90 for m∠RDB and the given expressions for m∠ JDR and m∠ BDJ into the equation. Then we can solve for y.
