Question 393286
 60 - 20 = 20 + _______ what is the answer. I need to explain to my 8 year old. 
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The answer is 20.
If I had to do this with an eight yr. old I would get a bunch of dimes.
I would make a group of 6 for the 60 (the left side of the equation)
and I would make a group of 2 for the 20 (the right side of the equation.
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I would form a "bank" of several dimes away from the two "groups".
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I would ask the 8 yr old to remove 20 from the left side and
put it in the bank.
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I would ask the 8 yr old to take enough from the bank so the group
on the right equaled the group on the left.
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If that did not answer the question you have posted, I would run
through the whole process again till the answer was seen.
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If you are looking for an algebric method go through the following.
60 - 20 = 20 + _______ what is the answer
Explain the the right side must balance the left side of the equal side
Evaluate the left side to get 40.
Ask what needs to be added to the right side so it will balance the 40
on the left.
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Good luck.
Cheers,
Stan H.