Answer:
Step-by-step explanation:
Part A
Cost = T - (15/100) * T
Cost = (85/100)*T
Part B
You are asked to take 15% off the cost of something. The first equation is very clear how to do that -- just take 15% of T away from T
The second part is not so obvious if you are not familiar with it, but the result will be the same.
Start with the first equation
Cost = T - (15/100) T Change 1 T to 100 / 100
Cost = 100*T/100T - 15/100T
Cost = 85 /100 * T
Part C
Cost = Phone - 14 at Top quality. Red in Graph below
Cost = 75/100 * Phone at Big value. Blue in Graph belos
The graph below is a good way to answer this. I won't solve it algebraically when the graph will give you a much better idea which phone to get.
Answer: Up to a phone cost of 55 dollars, the red phone is the better buy.
After 55$ the blue phone is better.
Try this with a couple of values for phone,
