You need to add all of these values together. This is 2 + 9 + 4 which gives 15
There are 180° in a triangle. Divide this by 15.
180/15 = 12
Then multiply this by the largest in the ratio; which is 9.
This is 12 x 9 which = 108°.
The largest angle is therefore 108°.
For reference, the ratio in degrees would look like this:
24:108:48, which adds up to 180°.