Answer:
$646.25 is her earnings when selling $975.
Her earnings when selling $x is 500 + 0.15x.
Explanation:
You know that her guaranteed salary is $500, and she also gets a commission that is 15% of her sales. So, the expression is
500 + 0.15x
Where x is total sales. When you are given $975 as her total sales, plug it in for x:
500 + 0.15(975)
500 + 146.25
$646.25 is her earnings when selling $975.
Her earnings when selling $x is 500 + 0.15x.