If the sum of interior angle measures of a polygon is 900 how many sides does the polygon have?

the polygon is *heptagon (7-sided polygon)
Sum of interior angles is ##180(n-2)##
Since sum is ##=900##
##900=180(n-2)##
##900/180=(180(n-2))/180##
##900/180=(cancel180(n-2))/cancel180##
##5=n-2##
##5+2=n##
##7=n##