Answer:
1.00304 * 10^10
Step-by-step explanation:
The first one dark blue I think
Double facts the even and odd numbers for example 2×2=4
Using the fundamental counting theorem, we have that:
- 648 different area codes are possible with this rule.
- There are 6,480,000,000 possible 10-digit phone numbers.
- The amount of possible phone numbers is greater than 400,000,000, thus, there are enough possible phone numbers.
The fundamental counting principle states that if there are p ways to do a thing, and q ways to do another thing, and these two things are independent, there are ways to do both things.
For the area code:
- 8 options for the first digit.
- 9 options for the second and third.
Thus:

648 different area codes are possible with this rule.
For the number of 10-digit phone numbers:
- 7 digits, each with 10 options.
- 648 different area codes.
Then

There are 6,480,000,000 possible 10-digit phone numbers.
The amount of possible phone numbers is greater than 400,000,000, thus, there are enough possible phone numbers.
A similar problem is given at brainly.com/question/24067651
7 1/12 - 2 3/4
First we have to change mixed numbers to improper fractions
7 1/12 = 7 x 12 + 1 = 85 85/12
2 3/4 = 2 x 4 + 3 = 11 11/4
85/12 - 11/4
Now we need to find the LCD (least common denominator) for 4 and 12
4, 8, 12
12
12 is our LCD, so it becomes our new denominator
85/12 would stay the same because the denominator wasn't changed but for 11/4 our new denominator is 12, so our fraction will change.
11/4 = 33/12
4 goes into 12, 3 times. What you do to the bottom, you do to the top.
3 x 11 = 33
3 x 4 = 12
So, our new fraction is 33/12. Now we subtract
85/12 - 33/12 = 52/12
Now we convert back to a mixed number
52 ÷ 12 = 4 4/12 reduce
4 1/3
Hope this helps.