Answer:
Number of 1 $ bill = 20
Number of 5 $ bill = 6
Explanation:
Let p represent number of one dollar bolls and q represent number of five bills.
A total of 26 bills are in a cash box.
p + q = 26 ------------------------- Equation 1
The total amount of cash in the box is $50
p + 5q = 50 ------------------------- Equation 2
Equation 2 - Equation 1,
p + 5q - p -q = 50 - 26
4q = 24
q = 6
Substituting in equation 1.
p + 6 = 26
p = 20
Number of 1 $ bill = 20
Number of 5 $ bill = 6
I think it's C, because first you multiply all the sides which is 112 then multiply by 3 and the answer it's 336 if I'm correct.
I used 3.14 for pi to solve easier.
6. 6.28
7. 21.98
8. 94.2
The series 7 + 16 + 25 +34 +43 +52 + 61 is an illusration of arithmetic series
The sigma notation of the series is: 
<h3>How to write the series in sigma notation?</h3>
The series is given as:
7 + 16 + 25 +34 +43 +52 + 61
The above series is an arithmetic series, with the following parameters
- First term, a = 7
- Common difference, d = 9
- Number of terms, n = 7
Start by calculating the nth term using:
a(n) = a + (n - 1) * d
This gives
a(n) = 7 + (n - 1) * 9
Evaluate the product
a(n) = 7 - 9 + 9n
Evaluate the difference
a(n) = 9n - 2
So, the sigma notation is:

Read more about arithmetic series at:
brainly.com/question/6561461