The numbers of new CDs is 30 and the old CDs is 21.
To solve this problem, we have to write a system of equations in which we would know the numbers of each types of CD she bought.
<h3>System of Equations</h3>This is used to solve a series or complex of word problems in which we can represent in a mathematical statements;
- Let n represents numbers of new CDs
- Let u represents numbers of old CDs
The equations can be represented as
Let's take equation (i)
Making n the subject of formula
we can put equation (iii) into equation (ii)
Let's put the value of u into equation (i)
From the calculations above, the numbers of new CDs is 30 and the old CDs is 21.
Learn more on system of equations here;