SOLUTION: What should be added to (-7/20) to get (-2/5)?

Question 754303: What should be added to (-7/20) to get (-2/5)?
Found 2 solutions by Alan3354, mgmoeab:
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
What should be added to (-7/20) to get (-2/5)?
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(-7/20) + what = (-2/5)
Subtract (-7/20) from both sides
what = (-2/5) - (-7/20)
Get a common denominator
what = (-8/20) - (-7/20)
- times - = +
what = (-8/20) + 7/20
Combine
what = -1/20

Answer by mgmoeab(37) (Show Source): You can put this solution on YOUR website!
Proceed as follows:
1. What are they asking you?
You need a NUMBER that once you add to it, you get
Now, let X be the number you dont know.
The question can be written as:
(a number plus gives me
SOLUTION:

This is the same as:

If you solve for X, you'll get:
(Notice how you have a negative (7/20) on the left side, and it turns positive on the right side)

This tells you that if you add to you'll get

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