First, its important that we review what types of shapes we have. In the first two problems, we have a cylinder. In the last problem, we have a rectangle. The formulas for volume of a cylinder and a rectangle are:
Cylinder
V =

Rectangle
V = L x W x H
In the first problem, we have a cylinder and we are looking for the height. We know the volume (240), and we know the radius (4). We can use these values to fill in our formula, and then solve for the missing height. (This process is shown in the image).
In the second problem, we have a cylinder and we are looking for the volume. We know the radius (4), and we know the height (12). We can use these values to fill in our formula, and then solve for the volume. (This process is shown in the image).
In the third problem, we have a rectangle and we are looking for the length. We know the height (10), we know the width (4), and we know the volume (200). We can use these values to fill in our formula, and then solve for the length. (This process is shown in the image).