If I give my brother $5$ dollars, then we will have the same amount of money. If instead he gives me $10$ dollars, then I'll have twice as much money as he will have. How much money does my brother currently have (in dollars)?
Amt you have at first = A
Amt your brother has at first = B
After you give him $5
A - 5 = B + 5
A = B + 10 (1)
If he gives you $10
A + 10 = 2(B - 10)
(B + 10) + 10 = 2B - 20
B + 20 = 2B - 20
B = 40
He has $40
You have $50
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