That is, we're interested in flight times that lie within 2 standard deviations of the mean. The empirical rule tells us that 95% of the distribution lies within 2 standard deviations of the mean.
Given m ∠ Q P S = 4 7 ∘ m∠QPS=47 ∘ m, angle, Q, P, S, equals, 47, degrees m ∠ R P S = 3 x − 3 8 ∘ m∠RPS=3x−38 ∘ m, angle, R, P, S, equals, 3, x, minus, 38, degrees m ∠ Q P R = 7 x − 9 5 ∘ m∠QPR=7x−95 ∘