6 (ab) - (6a) b
What’s the property

If i drew it correctly, then al would also equal 14 in., because the midsegment divides the line ab into 2, equal in length lines.therefore, al = lb 

That little box would be 90 degrees. a triangle should be 180 degrees. 90 + 15= 105. 180-105=75. your answer would be 75 degrees but since you asked for the nearest tenth, it would be 80 degrees.