Using the probability concept, the number of blue balls you need to add is:
D) 5.
<h3>What is a probability?</h3>
A probability is given by the <u>number of desired outcomes divided by the number of total outcomes</u>.
A probability of 0.5 is reached if the number of red balls is the same as the number of blue balls. Current the difference is of 7 - 2 = 5, hence 5 blue balls must be added.
Given that the insurance pays 80% of the cost of surgery and the surgery cost $9600, the amount of money Vivian will pay will be given as follows: 20/100×9600 =$1960 since she will cater for the deductibles that amount to $500 before the insurance takes over, then the total amount she will have to pay will be: 1960+500 =$2420