Answer:
x = 26.5
Step-by-step explanation:
Step 1: Write equation
(t + 10.5) + 2t + 90 = 180
Step 2: Solve for <em>t</em>
<u>Combine like terms:</u> 3t + 100.5 = 180
<u>Subtract 100.5 on both sides:</u> 3t = 79.5
<u>Divide both sides by 3:</u> t = 26.5
Step 3: Check
<em>Plug in x to verify it's a solution.</em>
<u>Substitute:</u> (26.5 + 10.5) + 2(26.5) + 90 = 180
<u>Parenthesis:</u> 37 + 56 + 90 = 180
<u>Add:</u> 180 = 180
∴ x = 26.5
Answer:
The best estimate of the number of times out of 39 that Ariana is on time to class is 27.
Step-by-step explanation:
For each class, there are only two possible outcomes. Either Ariana is on time, or she is not. The probability of Ariana being on time for a class is independent of other classes. So we use the binomial probability distribution to solve this question.
Binomial probability distribution
Probability of exactly x sucesses on n repeated trials, with p probability.
The expected value of the binomial distribution is:

The probability that Ariana is on time for a given class is 69 percent.
This means that 
If there are 39 classes during the semester, what is the best estimate of the number of times out of 39 that Ariana is on time to class
This is E(X) when n = 39. So

Rounding
The best estimate of the number of times out of 39 that Ariana is on time to class is 27.
Im not sure if it’s right but I think it’s -6,17
7.5 = x +

equals
x = 6.
First, subtract

from both sides. / Your problem should look like: 7.5 -

= x.
Second, simplify 7.5 -

to 6. / Your problem should look like: 6 = x.
Third, switch sides. / Your problem should look like x = 6, which is your answer.