The perimeter of the base of a regular quadrilateral prism is 60 cm, the area of a lateral face is 105 cm2. find: the volume of the prism

Since the base is a regular quadrilateral, each of its 4 sides must have length
  s = P/4
  s = (60 cm)/4 = 15 cm

The area of one lateral face is the product of side length and height.
  A = s×h
  105 cm² = (15 cm)×h
Then the height of the prism is
  h = (105 cm²)/(15 cm) = 7 cm

The area of the base is then
  B = s²
  B = (15 cm)² = 225 cm²

The volume of the prism is the product of its base area and height.
  V = Bh
  V = (225 cm²)×(7 cm) = 1575 cm³

The volume is 1575 cm³.