9. Area of a triangle is proportional to height. If the height increases by a factor of 4, then ...
The area will increase by a factor of 4. . . . . (2nd selection)
10. The base lengths and height are needed:
• 5 mm
• 8 mm
• 10 mm
Since the formula for the base of the cylinder is

, multiplying that by 10 we get

. Hope this helps!
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).
2-1/4
2/1=8/4 Multiply top and bottom by 4
8/4-1/4
7/4
1 3/4