Question

A bag contains only red, green, brown and yellow marbles.
The probabilities of selecting each colour are shown below.
The probability of choosing a red marble is the same as choosing a yellow marble.

Colour Red Green Brown Yellow
Probability 0.27 0.07
Find the probability of selecting a brown or yellow marble.

Answer 1

The probabilites must add up to 1

I will assume your "shown below" is:

Prob(red) = .27
prob(green) = .07
It said prob(yellow) equals prob(red), so prob(yellow) = .27

then prob(brown) = x
.27 + .07 + x + .27 = 1
x = .39

prob(brown or yellow) = .39 + .27 = ...