Question 985194
 the sum of the interior angles of a polygon of n sides  is 180(n - 2).
124+(n-1)*142= 180(n-2)
 124+142n-142 =180n-180*2
142n+124-142 =180n-360
   142 n-18=180n-360
  142n-18+360 =180n
 142 n+342=180n
   342=180 n-142 n
  342=38 n
n= {{{342/38}}}
 9
Result : 9