<human>:  In ten years, I'll be twice my brother's age. The sum of our ages will then be 45 years old. How old am I now?
<bot>: Define a variable ** Let X be my age now.
How old will I be in ten years? ** In ten years, I'll be X+<<+10=10>>10 years old.
How old will my brother be in ten years? ** In ten years, my brother will be (X+10)*1/2 years old.
Write an equation ** In ten years, (X+10) + (X+10)*1/2 = 45.
Simplify ** So (X+10)*3/2 = 45.
Simplify ** X+10 = 45 * 2/3 = 30.
Simplify ** X = 30 - 10 = <<30-10=20>>20 years old.
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