Answer:
64.8°
Explanation:
in the given ratio 9:13:3 the required middle angle is presented as 9;
1) if the sum of the angles of triangle is 180, then the given ratio can be re-written as
9x+13x+3x=180, ⇒ x=36/5;
2) if x=36/5, then the required measure of the middle angle can be calculated:
m(∠MIDDLE)=9*36/5=64.8°.