Answer: Choice D
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Explanation:
The formula for the surface area of a cylinder is

We then replace r with 10 and h with 25. Keep in mind that the diameter is 20 mm, so the radius is half that at 10 mm.
So that's how we get to

The tie was marked down by 40%
To solve 7-2a-5-14=-2+3a :
1) combine like terms: 7-19 - 2a = -2 + 3a, and then -10 = 5a
2) solve this equation for a: a = -10/5 = -2.
The solution of 7-2a-5-14=-2+3a is a = -2.