Answer:
17 white sweatshirts were sold and 19 yellow sweatshirts were sold.
Step-by-step explanation:
Let <em>w</em> represent the number of white sweatshirts sold and <em>y</em> represent the number of yellow sweatshirts sold.
We can write a system of equations to represent the situation.
Since the store sold a total of 36 sweatshirts, the sum of the white and yellow sweatshirts must total 36. So:

And since each white sweatshirt cost $10.95 and each yellow sweatshirt cost $11.50 and the total profit was $404.65:

Solve the system. I'll use substitution this time (though elimination will work just as perfect). From the first equation, subtract <em>w</em> from both sides:

Substitute this into the second:

Distribute:

Simplify:

Divide both sides by -0.55:

So, 17 white sweatshirts were sold.
Using the modified equation, substitute:

Therefore, 17 white sweatshirts were sold and 19 yellow sweatshirts were sold.