<span>Triangle ACD is similar to triangle ABD</span>
Assuming that each marble can be picked with equal probability, we notice that there is a total of

marbles, of which 2 are red.
So, the probability of picking a red marble is

In fact, as in any other case of (finite) equidistribution, we used the formula

Answer:
x = 30
Step-by-step explanation:
Put in proportions
= 
Cross multiply and get 27x = 45 x 18
OR...
27x = 810.
THEN...
divide by 27 on both sides to get 30
x = 30
Answer : 4.485
I’m pretty sure I just went with someone else answer !