Answer: $73
Explanation
x = amount of money you start with
y = amount of money your brother starts with
Giving your brother $8 will decrease your amount to x-8.
Meanwhile his amount will increase to y+8.
At this point the two amounts are equal.
x-8 = y+8
x-8-8 = y
y = x-16
We'll substitute this into another equation.
If instead your brother gives you $19, then your amount increases to x+19 and his amount drops to y-19.
At this point your amount is twice that of his.
your amount = 2*(his amount)
x+19 = 2*(y-19)
x+19 = 2*(x-16-19) ....... plug in y = x-16
x+19 = 2*(x-35)
x+19 = 2x-70
x-2x = -70-19
-x = -89
x = 89 dollars is what you started with.
y = x-16
y = 89-16
y = 73 dollars is what your brother started with.
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Check:
If you give him $8, thenyour amount = 89-8 = 81
his amount = 73+8 = 81
Showing you both would end up with the same amount of money ($81)
This verifies the first condition.
If he gives you $19, then your amount = 89+19 = 108
his amount = 73-19 = 54
Notice that 108 is twice that of 54
54*2 = 108
Both conditions have been verified.