Answer:

Step-by-step explanation:
Hello, I can help you with this
Step 1
define
The minimum weekly commission earned to be a STAR sales person is $9000, let's name this value as M
if Sandra receives a 12% commisions of the sale of all cars, then that 12% must be equal or higher than 9000 in order to become a STAR sales person
Step 2
using a rule of three find the 100%
if
12% ⇔ $9000
then
100% ⇔x
the ratio is

Now, solve for x

so, Sandra must sell a minimun of $75000
Now, to give a response, we need to asume a only price for every car(p).
now, in matemathical terms.
the minimun number of cars she must to sell is
minum number of cars sandra has to sell to become a STAR sales person
is 

now, price of the car* number of the car = 75000
where

Have a nice day