Help pleas brainliest promised if right

Ineed to learn how to solve this problem

Find the perimeter of the triangle with vertices  d(3, 4),  e(8, 7), and  f(5, 9). do not round before calculating the perimeter. after calculating the perimeter, round your answer to the nearest tenth.  

Even if a person is in very good shape, applying to be a police officer requires commitment to fitness. applicants must pass a physical fitness test. in order to prepare for the test, janet purchases an activity tracker to court her steps. her goal is to walk 10,000 steps each day. she measures heard average step length to be 30 inches. play janet runs, her average steps length increases to 36 in. how many steps would she have to take to run 1 mile 50280 round to the nearest step