Your answer on #3 was on the right track.
She starts with $50.
After one visit, she'd have $50 - $3.75.
After a second visit, she'd have $50-$3.75 - another $3.75.
So after three visits, you'd have subtracted three $3.75's.
After three visits, you'd have subtracted four $3.75's.
Going with their "b" and "n" variables:
b = 50 - 3.75n
Notice the balance is going down the more she goes.
On #4, approach it the same way by working out a couple of "after 1 hour, after 2 hours, after 3 hours" scenarios and see if you can build up the equation.
If you post back what you think the answer is on #4, I'll say if it's right or not.-
-------- updated----
I missed the other pictures originaily, so this bit continues on with those.
On picture #2, with the pages read after so many hours....
To figure out how many pages per hour this person is reading, you need to compare how many were read after 1 and 4 hours.
The person had 644 pages left after 1 hours and 500 pages left after 4 hours. This means in that three hour window, they read 644-500 = 144 pages.
144 pages over 3 hours = 144/3 pages per hour, or 48 pages per hour.
Given that they're reading 48 pages per hour and there were 644 pages remaining after 1 hour of reading, how many pages did they start with?
With all this new info now, what do you think about the third statement?
And picture #3:
Your equation looks good. What does the $20 represent and what does the $60 represent in your equation?
In the bigger picture, what do the x-values and separately what do the y-values represent?
