ANSWER
0.9738 or 97.38%
EXPLANATION
Given:

Desired Outcome:
Probability that it will last 10 years
z-score for the sample:

p-value
For the z-score of 1.9376, the p-value is 0.9738 or 97.38%
Hence, the probability that it will last longer than 10 years if you randonly purchase one item is 97.38%
Hi there! The answer is B.

First we work out the parenthesis, which is easy because we can just remove them.

Now rearrange our expression (in order to collect terms later).

Next up is collecting the terms.

The answer is B.
~ Hope this helps you!
0.10r + 0.20b = 24
3r = b + 20....b = 3r - 20
0.10r + 0.20(3r - 20) = 24
0.10r + 0.60r - 4 = 24
0.70r = 24 + 4
0.70r = 28
r = 28/0.70
r = 40 <=== there are 40 reds
0.10r + 0.20b = 24
0.10(40) + 0.20b = 24
4 + 0.20b = 24
0.20b = 24 - 4
0.20b = 20
b = 20/0.20
b = 100 <=== there are 100 blues