Let's use the variable 'm' to represent the number of magazines sold.
If they make 1.25 per magazine sold, the total revenue is the product of the unitary value of one magazine by the number of magazines sold:
The costs are the values of 100 and 150, so we have:
Finally, the profit they want to have is at least 3000, so:
If the profit is calculated by the revenue minus the cost, we have that: