A study by a group of cardiologists determined that maximal heart rate in humans, a parameter used as a basis for prescribing exercise programs, depends on age. Maximal heart rate is around 201 beats per minute for a 10-year-old, and decreases at a constant rate of 7 every 10 years. Which of the following inequalities best describes the ages, for which maximal heart rate is less than 180, a is >or equal to 10.. HELP