Answer:
A is the correct equation to use when solving this problem
The least number of cars she can wash is 15
Explanation:
If "'x" is the number of cars Emilia washes, then we would need to multiply that by the amount of money she gets from each car which means that "14x" needs to be in the equation somewhere. From this, we can already rule out C and D because those don't have "14x".
Also, since it says that Emilia needs at least $240, that would mean that she needs $240 or higher. Since the sign in equation A shows that, we know that it is equation A.
Since Emilia needs $240 or higher, the least number of cars she could wash would need to give her enough money to get to $240 when added to the $30 Emilia already has. We can multiply 14 by 15 to give us 210 which when added to the $30 she already has, will give us $240 which is the minimum amount of money she needs to buy new headphones.
(I'm sorry this is so confusing. I'm not good with words but I hope this helped)