SOLUTION: Four CDs and three DVDs cost €108, while one DVD and three CDs cost €56. Find the cost of a CD and the cost of a DVD. Let c = cost of a CD d = cost of a DVD.

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: Four CDs and three DVDs cost €108, while one DVD and three CDs cost €56. Find the cost of a CD and the cost of a DVD. Let c = cost of a CD d = cost of a DVD.      Log On


   

Question 985202: Four CDs and three DVDs cost €108, while one DVD and three CDs cost €56.
Find the cost of a CD and the cost of a DVD.
Let c = cost of a CD
d = cost of a DVD.
Answer by srinivas.g(540) About Me  (Show Source):
You can put this solution on YOUR website!
et c = cost of a CD
d = cost of a DVD
Four CDs and three DVDs cost €108
4c+3d =108........(1)
one DVD and three CDs cost €56
3c+d=56...........(2)
Solved by pluggable solver: SOLVE linear system by SUBSTITUTION
Solve:
+system%28+%0D%0A++++4%5Cc+%2B+3%5Cd+=+108%2C%0D%0A++++3%5Cc+%2B+1%5Cd+=+56+%29%0D%0A++We'll use substitution. After moving 3*d to the right, we get:
4%2Ac+=+108+-+3%2Ad, or c+=+108%2F4+-+3%2Ad%2F4. Substitute that
into another equation:
3%2A%28108%2F4+-+3%2Ad%2F4%29+%2B+1%5Cd+=+56 and simplify: So, we know that d=20. Since c+=+108%2F4+-+3%2Ad%2F4, c=12.

Answer: system%28+c=12%2C+d=20+%29.