Ekua designs and sells T-shirts for $13 each

First we have to see both side of the inequality. On the left side we can add the t-shirts Ekua sells. Which is $13 for each. Since they said let t represent the number of t shirt she sells, our inequality looks like this:

13t ≥

Now we need to add our fixed costs, she spends $280 each month plus $9.50 per t shirt.

$13t ≥ 280 + $9.50t

Now we move the costs to one side. We'll move $9.50 to the left so we can easily subtract:

$13t - $9.50t ≥ 280

Solve the left side:

$3.5t ≥ 280

To solve for t we divide 3.5 from both sides:

$3.5/3.5t ≥ 280/3.5

We get:

t ≥ 80

Hope this helps :)