Suppose there is a box of balls, 30% blue, 15% red, 45% orange and the rest black ( %10)

a) What is the probability that a randomly selected ball is either blue or red

b) What is the probability that a non-black ball is blue ?

For part a)
 `P(A + B) = 30 + 15 = 45%` is what i think, but im not sure if i need to use the

```
           P(A + B) = P(A) + P(B) - P(AB) formula ?

```

for part b)
 The chance of getting a non-black ball is 90%, but how do i get the probability of blue balls knowing this

Any tips or hints when it comes to thinking about these problemss?