Find the height of a rectangular prism if the volume is 171 in, the length is 6 in, and the width is 4 3/4.

Geometry ? i don't know how to do any of these.

Find three consecutive numbers such that the sum of one-fourth the first and one-fifth the second is five less than one-seventh the third

David is spreading mulch on a triangular area of his flower bed. the coordinates of the vertices of the area are (1, 3), (9, 3), and (4, 6). what is the area of the triangle if each square has an area of 3 square feet?