In a theater there are 15 chairs in the first row, each row has 3 more chairs than the previous row, and there are 17 rows. How many chairs are in the theater?​

The point of intersection of the diagonals of a rectangle is 4 cm further away from the smaller side then from the larger side of the rectangle. the perimeter of the rectangle is equal to 56 cm. find the lengths of the sides of the rectangle. 16 points answer quick