First, write the given situation as a linear equation, as follow:
[tex]C(n)=1,000+300n[/tex]where C(n) is the money Alex earns per month and n is the number of cars He sells.
We wrote 1,000 because it is the fixed money per month Alex earns and 300n because he earns 300 for each sold car.
In order to determine the number of cars n for a total earnings of $16,000, replace C = 16,000 and solve for n, as follow:
[tex]\begin{gathered} 16000=1,000+300n \\ 16,000-1,000=300n \\ 15,000=300n \\ n=\frac{15,000}{300} \\ n=50 \end{gathered}[/tex]Hence, Alex sold 50 cars in order to earn $16,000 last month
