Question

A student bought 1 Blu-Ray and 2 DVD movies for a total of $90, while a second student spent $171 to purchase 5 DVDs and 1 Blu-Ray. If B is the cost of a Blu-Ray in dollars and D is the cost of a DVD in dollars:
a) Write two (2) equations that relate the number of Blu-Rays and DVDs to their cost.
b)Solve the above equations simultaneously to find the cost of a Blu-Ray and the cost of a DVD.
c) Check your solution.

Answer 1

Let Blue Ray = b and let DVD = d

If they bought 1 blue ray and 2 dvds for 90 that looks like

b + 2d = 90

Now if another student bought 5 dvds and 1 blue ray for 171....that is

b + 5d = 171

So we have our 2 equations

\[\large b + 2d = 90\]\[\large b + 5d = 171\]

Answer 2

So far I have only dealt with one letter in a questions, how do I go about solving these ?

Answer 3

Oh okay...well then this is good that we have 2 equations then....

When you have more than 1 variable...(2 here)you need that many equations (2) to solve for it...

Alright....so choose 1....elimination method (easier here) or substitution method

Answer 4

uhm i dont know the difference so do the easier elimination

Answer 5

Lol alright...and both are ways to solve systems of equations here...(I'll do substitution later so you can see it too :)

So elimination...the process of eliminating 1 variable so you can solve for the other...

Start with both equations

\[\large b + 2d = 90\]\[\large b + 5d = 171\]

Answer 6

Now subtract them...

Why? because if you look...if you were to subtract the 2 equations up there....the 'b' variable would go away (eliminated) because b - b is 0

Answer 7

what are we subtracting ?