A bad contains 15 balls of which X is red. Write an expression for the probability that a ball drawn from the bad is red. When 5 more red balls are added to the bag, the probability becomes 3/4. Find the value of X.

Answer:
10
Step-by-step explanation:
The current probability of picking a red ball is [tex]\frac{x}{15}[/tex]. When 5 more balls are added, the probability is 3/4. We can write a ratio for this problem:
[tex]\frac{x+5}{15+5} = \frac{3}{4}[/tex]
When using cross multiplication to solve this, you get 3 * 20 = 4(x+5).
60 = 4x + 20
40 = 4x
x = 10 red balls