Given:
Anna’s cell phone plan charges her $30 per month plus a $150 one-time activation fee.
Evelyn’s cell phone plan charges her $20 per month, plus a $450 one-time activation fee.
To find:
The number of months after which the costs for the girls’ cell phone plans the same.
Solution:
Let x be the number of months.
Total cost = Fixed cost + Variable cost
According to the question, cost equation for Anna’s cell phone is
...(i)
Cost equation for Evelyn's cell phone is
...(ii)
Equate (i) and (ii) to find the time after which the costs for the girls’ cell phone plans the same.
Divide both sides by 10.
Therefore, the costs for the girls’ cell phone plans the same after 10 months.
There is a lot to go over here. Unfortunately it looks like you got a lot incorrect. I'll focus on two problems. Hopefully these examples below will help correct the other mistakes.
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Problem 7)
We have the starting value be 20 and the ending value be 11. Subtract the values: (end)-(start) = 11 - 20 = -9. The negative indicates we have a drop or decrease.
We'll focus on the positive version of this number, so 9. Divide this value over the starting amount 20 to get 9/20 = 0.45 = 45%
So going from 20 miles to 11 miles is a decrease of 45%
Answer to problem 7 is: 45%
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Problem 13)
An increase of 300% means we added 3 times the original amount onto the original amount.
We take 300% of 25 to get 3*25 = 75
Which is then added onto 25 to get 25+75 = 100
Answer to problem 13 is: 100
I think it would be most likely A the first one.
You do 40 times 15 that would be 600