Question

Find the number of sides of a convex polygon in which 3 of the angles are 130 degrees

Answer 1

let the number of sides be n , n is a whole number so that n> 3
the sum of the exterior angles of any convex polygon add up to 360°

So far we have 3 exterior angles of 50° each or a total of 150°
leaving exterior angles of sum 210°
Your polygon could not have been a regular pentagon, since
360/50 is not a whole number

There is no unique solution to your problem, perhaps some more
information was given?

e.g. it is a pentagon , n = 5
the other 2 interior angle could have been 70° and 80° (70+80=150)
or they could have been 100° and 50°
or ....

e.g. it is a hexagon, n = 6
the other 3 exterior angles could have been 70°, 70°, 70°
(sum of exterior angles: 70+70+70 + 50+50+50 = 360)
etc