Robert bought X pounds of potatoes for $1.99 per pound. He paid for the potatoes with a $10 bill. Which of the following variable expressions represents the amount of change he received from his $10?

a. 10 - 1.99x

b. 1.99x - 10

c. 10 - 1.99 = 8.01

d. 10 - x = 1.99

First, we have to figure out the expression for the total price of potatoes. We find that by multiplying the price of potatoes per pound by how many pounds were bought. Robert bought x pounds of potatoes at $1.99 per pound. This can be written as:

$1.99x

Next, we have to find the equation for Robert's change. Change is defined as amount paid minus cost. In this scenario, Robert paid $10, and we already know the cost is $1.99x. So using this information, we can now write the equation:

$10 - $1.99x

So the answer is a.