let the number of sides be n.
now we know that
the sum of interior angles = 180*(n-2)
since we have 5 right angles the sum is 5*90 = 450 and the remaining sides are 195 degrees each
hence 450 + 195(n-5) = 180*(n-2)
450 + 195n - 975 = 180n - 360 which follows
15n = 165
n = 11
therefore the number of sides is 11