You could do :
Johnny was financing a limited editions Xbox One S. The price was $420 and he put down 40%. How much is left to be financed?
dp=420(40/100)=16800/100=168
then you would subtract 420-168 which would give you 252
;) good luck !!
Answer: 
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Work Shown:

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Explanation:
The idea is to first get all the y terms to one side. I did this by subtracting 2y from both sides in the third step.
Then factor out y and divide both sides by (8x-2)
Afterward there's the optional steps of simplifying (as shown in the final two steps).
Answer:
Slope=2/10 or 0.2
Step-by-step explanation:
First, pick the numbers you want to use for slope. I will be using -10 as x1, 0 as x2, -1 and y1, and 1 for y2. The formula for slope is y2-y1/x2-x1.
Plug in these numbers: 1+1 (two negatives make a positive)/0+10(again, two negatives combine to make a positive)
This makes 2/10, which divided eaquals 0.2.
You can use either 2/10 or 0.2 as your answer, depending on what your teacher requires. Have a nice day and let me know if you have any questions!! :)