ANSWER:
150 coins
STEP-BY-STEP EXPLANATION:
We know that of the total that the pirate initially had 2/3 I keep them in a chest and the rest he distributed, the rest corresponds to 1/3 of the total.
Now, if each one received 25 coins, and 3 three members, it means that 1/3 is equivalent to 3 times 25 coins, that is, 75 coins.
Now, if 1/3 is 75 coins, 2/3 proportionally would be:
[tex]\begin{gathered} \frac{75}{\frac{1}{3}}=\frac{x}{\frac{2}{3}} \\ \text{ solving for x} \\ 225=\frac{3x}{2} \\ x=\frac{225}{3}\cdot2 \\ x=150 \end{gathered}[/tex]Which means that the pirate kept 150 coins in the chest