Activity Vivian is at a falr In Coachella Valley, California. Much of the valley lies below sea level. Vivian has brought along an altimeter to measure her
elevation at different places in the valley. Vivian's first ride was on the Ferris wheel. When she sat on the wheel at its lowest point, her altimeter
read -9.6 feet. When she reached the top of the wheel, her altimeter read 12.3 feet.
Complete the following steps to calculate the change in Vivian's elevation from the bottom of the Ferris wheel to the top.