The answer is B. You add all the numbers together and divide by the amount of numbers you have to find the mean. The missing height is 62 because 54+57+59+63+66+68+70+58=563 563/9 (amount of numbers you have including the missing height) = 63
First, convert 2 meters into cm and then convert to mm. m to cm+200cm cm-mm= 2000. Then turn 86 centimetres into mm which is 860 mm. Lastly 2000+860=2860. Hope this helps