Mary sells fax machines which come in Standard and Enhanced models. The Standard model sells for $230 and the Enhanced model sells for $305. If Mary sold a total of 31 units and took in $7,730, how many of the Enhanced model did she sell?

Do not enter units.

If she sells x of the $305 models, then the rest (31-x) are $230. So, now just add up the values.

305x + 230(31-x) = 7730

and find x

To find out how many of the Enhanced model Mary sold, we can set up a system of equations based on the given information.

Let's assume Mary sold x units of the Standard model and y units of the Enhanced model.

The given information tells us two things:
1. The total number of units she sold: x + y = 31
2. The total amount of money she made: 230x + 305y = 7,730

To solve this system of equations, we can use the method of substitution or elimination.

Let's solve it using the method of substitution:

From the first equation, we can express x in terms of y: x = 31 - y

Substitute this expression for x in the second equation:
230(31 - y) + 305y = 7,730

Now let's simplify the equation:
7,130 - 230y + 305y = 7,730
75y = 600
y = 8

Therefore, Mary sold 8 units of the Enhanced model.