Please help I've ask this same question and none are answering

Perform the indicated operation. 8/a - 6/a + 7/a

(b) suppose that consolidated power decides to use a level of significance of α = .05, and suppose a random sample of 100 temperature readings is obtained. if the sample mean of the 100 temperature readings is x⎯⎯ = 60.990, test h0 versus ha and determine whether the power plant should be shut down and the cooling system repaired. perform the hypothesis test by using a critical value and a p-value. assume σ = 5. (round your z to 2 decimal places and p-value to 4 decimal places.)

Find the rate of change for the situation.you run 7 miles in one hour and 21 miles in three hours.