Answer:
231
Explanation:
Let's consider that Gavin got X pounds.
Then Henry gets 3 times as much as Gavin => 3X
And Mark gets twice as much as Henry => 2 * 3X
Together they get 770, so:
X + 3X + 2*3X = 770
10X = 770 => X = 77
As we mentioned, Henry gets 3X, so
3X = 3 * 77 = 231