A DVD costs twice as much as a music CD. Jack buys 2 DVDs and 2 CDs and spends $45. Determine how much one CD costs, in dollars. [Only an alegbraic solution can receive full credit]
Let \(d=\) the cost of a DVD Let \(c=\) the cost of a CD
We have \(d=2c\) and \(2d+2c=45\)
We can replace \(d\) with \(2c\) in the second equation and get \(2(2c)+2c=45\) \(\rightarrow 4c+2c=45\) \(\rightarrow 6c=45\) \(\rightarrow c=7.5\rightarrow\$7.50\)
