Frist you do 6*13
Which equals 78
Then you do 8,500/78
Which equals <span>108.974358974</span>
<span>Then you round it to 109</span>
<span>and there's your awnser</span>
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</span>
Angle 2=3, so angle 1=4 because angles ABC & BCD equal 90°. When you add together the angles of a triangle you get 180 and if you could put angle 1 and 4 together it would look like an upward version.
That is the best way I could describe it. Hope that helps.