Bonjour voici mon énoncé pouvez-vous m’aider s’il-vous-plaît ?

A box contains Dragibus of different colors: Black, White, Green and Yellow. Ellen is
going to choose one of them at random from the box.
The table shows each of the probabilities that Ellen will choose a black or White or
Yellow Dragibus.
Green
Color
Probability
Black
0,28
White
0,15
Yellow
0,33
1. Work out the probability that Ellen will choose a green Dragibus;
2. Work out the probability that Ellen will not choose a yellow Dragibus ;
3. The box contains 250 Dragibus. Estimate how many black Dragibus are in this
box.