3. shawna's bikes rents bikes for $19 plus $4 per hour. lea paid $39 to rent a bike. for how many hours did she rent the bike?

An energy drink company claims that its product increases students' memory levels. to support its claims, the company issues advertisements claiming that 8 out of 10 people (chosen randomly from across the country) who tried their product reported improved memory. the missing component in this study is a .