Final answer:
To calculate the snack vendor's weekly earnings, multiply her sales by the 4% commission rate and add the result to her $400 base salary. Her total earnings for a week with $1080 in sales would be $443.20, which would allow her to buy 110 magazines at $4 each.
Step-by-step explanation:
The subject of this question is Mathematics, and it involves calculating weekly earnings based on a fixed salary plus commission for sales. To determine the weekly pay including commission, you first find out the commission amount and then add it to the base salary.
The sales commission is 4% of the total sales amount. Therefore, for sales totaling $1080, the commission is 0.04 * $1080, which equals $43.20.
Now, add the commission to the base salary of $400 to find the total weekly pay. So, the total pay for the week is $400 + $43.20, which equals $443.20.
In the context of purchasing power, if magazines cost $4 each, the maximum number of magazines the vendor could buy with her weekly earnings is $443.20 / $4 per magazine, which would be 110 magazines.