the first one. The camera focuses on the audience
Let p be the prize of a pen and m the prize of a mechanical pencils. If you buy six pens and one mechanical pencil, you spend 6p+m. We know that this equals 9, because you get 1$ change from a 10$ bill.
Similarly, if you buy four pens and two mechanical pencils, you spend 4p+2m, which is 8$, because now you get a $2 change. Put these equation together in a system:

Now, if you multiply the first equation by 2, the system becomes

Subtract the second equation from the first:

Plug this value into the first equation to get

We can find the acceleration via

We have


Then by definition of average acceleration,

so that


We alternatively could have found the time without knowing the acceleration. Since acceleration is constant, the average velocity is

Then


2.47 + 7.1
7.1 + 2.47
9.57-7.1
9.57-2.47
Answer:
Step-by-step explanation:
2.72 is the unit rate