Final answer:
Sonia must make at least 5 sales to meet her expenses.
Step-by-step explanation:
To find out how many sales Sonia must make to meet her expenses, we can set up an equation. Let's assume she needs to make x sales. Since she earns at least $300 per sale, her earnings from sales would be 300x dollars. In addition, she receives a $75 commission on every sale, which means her commission earnings would be 75x dollars.
To meet her expenses of at least $1800, Sonia's total earnings from sales and commission should be greater than or equal to $1800. Therefore, the equation would be: 300x + 75x ≥ 1800.
Combining the like terms, we get 375x ≥ 1800. Dividing both sides of the inequality by 375, we find that x ≥ 4.8 (approximately).
Since x represents the number of sales, we need to round up to the nearest whole number because Sonia cannot make a fraction of a sale.
Therefore, Sonia must make at least 5 sales to meet her expenses.