A truck rental service charges $27.50 for a full tank of gas and $12 for each hour you rent the truck. Which rule gives the cost for x hours of renting a truck that comes with a full tank of gas?

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 .