Well first you would start by setting up with a proportion.
In total, the girls paid $54+$22= $76
Thus 1 sister contributed $54/$76=x/100
The other sister contributed $22/$76=x/76
For each proportion, cross-multiply and simplify to get the percentage. The percentage will be the x
Simplify 4^4 to 256
256 + 1/2 = 256.5
Simplify 256 + 1/2 to 513/2
513/2 = 256.5
Since both sides equal, there are infinitely many solutions.
Answer:
Part A:
The probability that all of the balls selected are white:

Part B:
The conditional probability that the die landed on 3 if all the balls selected are white:

Step-by-step explanation:
A is the event all balls are white.
D_i is the dice outcome.
Sine the die is fair:
for i∈{1,2,3,4,5,6}
In case of 10 black and 5 white balls:






Part A:
The probability that all of the balls selected are white:


Part B:
The conditional probability that the die landed on 3 if all the balls selected are white:
We have to find 
The data required is calculated above:

Answer:
x=21.
Step-by-step explanation:
First you distribute 3 to the parenthesis. You should get 3x-21=42 at this point. Then you add 21 to 42 to get 63. Here you should be at 3x=63. Divide 63 by 3 to get x=3