May someone help me with these last 2 questions much appreciated

Malia is observing the velocity of a cyclist at different times. after two hours, the velocity of the cyclist is 15 km/h. after five hours, the velocity of the cyclist is 12 km/h. part a: write an equation in two variables in the standard form that can be used to describe the velocity of the cyclist at different times. show your work and define the variables used. (5 points) part b: how can you graph the equations obtained in part a for the first 12 hours? (5 points) if you can try and make this as little confusing as you can

Element x decays radioactively with a half life of 8 minutes. if there are 450 grams of element x, how long, to the nearest tenth of a minute, would it take the element to decay to 37 grams?

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 .