From the curve, we can read the approximate (age, mass) pairs: (12, 900), (16, 3000), (20, 5100)
percent change of mass from the age of 12 to 16=(3000-900)/900 * 100%=2100/900 *100% percent change of mass from the age of 16 to 20=(5100-3000)/3000 * 100%=2100/3000 *100%