Answer:
13
Step-by-step explanation:
We have been given that mean = 21 and total number of hours = 8
Let the number of prescriptions filled during hour two be x
[tex]Mean = \frac{Sum\hspace{3}of\hspace{3}all\hspace{3}the\hspace{3}number\hspace{3}of \hspace{3}prescriptions}{Total\hspace{3}number\hspace{3}of\hspace{3}hours}[/tex]
[tex]21 = \frac{18+x+22+25+16+24+22+28}{8}[/tex]
[tex]21 = \frac{155+x}{8}[/tex]
Multiply both sides by 8
[tex]21 * 8= \frac{155+x}{8}*8[/tex]
Cancel out the 8's on the top and bottom of the right side
[tex]168= 155+x[/tex]
Subtract 155 from both side
168-155=155+x-155
Cancel out +155 and -155 from the right side
13 = x
Flip the sides
x = 13
So, the number of prescriptions filled during hour two = 13
