2.067 pesos colombianos es un dólar ($1.00) de estados unidos. sandra está en un centro comercial en colombia. ella compra un disco compacto por 31.005 pesos. ¿cuánto paga sandra en dólares por el disco compacto?

In order to find the amount in dollars Sandra paid for the compact disk (CD) we have to use the Rule of three. This is a mathematical rule to find out an amount that is with another quantity given in the same relation as other two also known.  

For example:

We already know 2,067 Colombian pesos is equivalent to $1 and that Sandra bought the CD for 31,005 Colombian pesos.

With this information we are able to stablish a relation between the Colombian pesos and the United States dollars, as follows:

2,067 Colombian pesos ----- $1

31,005 Colombian pesos -----X

And this is solved as follows:

Finally