Find the critical values X^2 1-a/2and X^2 a/2 for a 80% confidence level and a sample size of n = 10

What is the common difference in the following arithmetic sequence? 7,3,-1,-5

The krasnapolski is a top-of-the-line hotel in amsterdam, the netherlands. among their many services, they rent bicycles to guests. the bicycle checkout is open 24 hours per day 7 days per week and has 50 bicycles on hand. on average, 10 guests request a bicycle each day, arriving completely randomly at all times of the day during the spring and summer seasons. guests keep bicycles for four days on average, with a standard deviation of two days. how long does a guest on average have to wait for a bike? a. approximately 24 hours b. approximately 0.033 hours c. approximately 4 days d. approximately 47 minutes

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'