Ethan works at an electronics store as a salesperson. Ethan earns a 5% commission on the total dollar amount of all phone sales he makes, and earns a 4% commission on all computer sales. Ethan had twice as much in computer sales as he had in phone sales and earned a total of $117 in commission. Write a system of equations that could be used to determine the dollar amount of phone sales Ethan made and the dollar amount of computer sales he made. Define the variables that you use to write the system.

From the information given, the first equation would indicate that the comission of all phone sales plus the comission from all computer sales would be equal to 117, which is:

0.05x+0.04y=117, where:

x is the amount of all phone sales

y is the amount of all computer sales

Also, the statement indicates that Ethan had twice as much in computer sales as he had in phone sales, which would be:

y=2x

Now, you can replace y=2x in the first equation and solve for x:

0.05x+0.04(2x)=117

0.05x+0.08x=117

0.13x=117

x=117/0.13

x=900

Finally, you can replace the value of x in y=2x to find the value of y:

y=2(900)

y=1800