<PRE><B>Question 725369</B>
If there are m sides, then the angles sum up to 180(m-2) degrees

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There is 1 angle that is 80 degrees


There are m angles total, so this means that there are m-1 angles left (if one is already taken). These m-1 angles are all 160 degrees.


So


80 + 160(m-1) = 180(m-2)


Solve for m:


80+160(m-1)=180(m-2)


80+160m-160=180m-360


160m-80=180m-360


160m=180m-360+80


160m-180m=-360+80


-20m=-360+80


-20m=-280


m=(-280)/(-20)


m=14


So there are 14 sides (and 14 angles).
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