Which formula should be used to calculate the amount of paper needed?

Round 0.866 to the nearest hundredth

The random variable x is the number of occurrences of an event over an interval of ten minutes. it can be assumed that the probability of an occurrence is the same in any two-time periods of an equal length. it is known that the mean number of occurrences in ten minutes is 5.3. the appropriate probability distribution for the random variable

Solve this system of equations. 12x − 18y = 27 4x − 6y = 10