We want to write and solve a system of equations to model the given situation.
The answers are:
A)
y = 50 + 4*x
y = 17 + 7*x
B) after 11 weeks.
C) 94 subscribers.
First, we must find the two linear equations, we know that Robin has 50 subscribers and she gets another 4 per week.
Then for Robin, we can write:
y = R(x) = 50 + 4*x
The equation that models the number of subscribers that Robin has at week x.
Dimitri at the moment has 17 subscribers and wins 7 per week, then his equation is:
y = D(x) = 17 + 7*x
A) Then the system of equations is just:
y = 50 + 4*x
y = 17 + 7*x
B) Now we must solve the system.
Notice that in both equations we have y isolated, then we can write:
50 + 4*x = y = 17 + 7*x
50 + 4*x =17 + 7*x
Now we can solve this for x:
50 + 4*x =17 + 7*x
50 - 17 = 7*x - 4*x
33 = 3*x
33/3 = 11 = x
This means that at week 11 they will have the same number of subscribers.
C) To get this we just need to evaluate any one of the two linear equations in x = 11
D(11) = 17 + 7*11 = 94
Both of them will have 94 subscribers.
If you want to learn more about systems of equations, you can read:
https://brainly.com/question/13984867
