In five years, Rehana will be three times as old as Phoebe. If Rehana is currently 25 years old, and Jacob, Rehana's brother, is 3/5 of Phoebe's current age, how old is Jacob now? Let's think first. Chain of thought:
If Rehana is currently 25 years old, she will be 25 + 5 = 30 in five years. Rehana will be three times as old as Phoebe in five years, meaning Phoebe will be 30 / 3 = 10 years old in five years. Currently, Phoebe is 10 - 5 = 5 years old. 3 / 5 of Phoebe's age now is 3 / 5 * 5 = 3 years, which is Jacob's age.
Therefore, the answer is 3.