Question

sum of all the angle of a convex polygon which has 7 sides

Answer 1

Sum of exterior angles = 360°
Sum of interior angles = (180° {n-2})°   [where n is no. of sides]
                                    = 180 X (7-2)
                                    = 180 X 5
                                    = 900°
Therefore the sum of interior angles is 900°

Answer 2

sum of exterior angles for every polygon is 360
sum of interior angles will be =180(n-2)
where n belongs to number of sides of the polygon...
solving the above equation we get the answer =900
hope my answer is helpful to u