David’s monthly salary is $2500 plus 6% commission on his sales. What must be the amount of his sales for him to earn at least $3,100 each month?

2500 + .06s ≥ 3100 , where s is his sales

.06s ≥ 600
s ≥ 600/.06
s ≥ 10,000

To determine the amount of sales David needs to earn at least $3,100 each month, we can set up an equation:

Let's denote the amount of sales as 'x'.

Commission on sales = 6% of x = 0.06x

Total monthly earnings = Salary + Commission

Based on the given information:

Total monthly earnings ≥ $3,100

Therefore, our equation becomes:

$2500 + 0.06x ≥ $3,100

To solve this inequality for 'x', we need to isolate 'x' on one side of the equation. First, let's subtract $2500 from both sides:

0.06x ≥ $3,100 - $2500

0.06x ≥ $600

Next, divide both sides by 0.06:

x ≥ $600 / 0.06

x ≥ $10,000

Therefore, David must have sales of at least $10,000 each month to earn at least $3,100.