Question 831089
In a regular octagon, there are 8 angles at 135 degrees for a total of 1080 degrees.
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You have an odd shaped one, an irregular octagon!  But the interior angles still need to equal 1080.  So, the 4 remaining angles need to total 1080 - 60 or 1020.
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See http://www.mathcaptain.com/geometry/octagon.html#irregular-octagon for more information.