Answer:
12
Step-by-step explanation:
The Mean is the average of the numbers: a calculated "central" value of a set of numbers.
To calculate it:
• add up all the numbers,
• then divide by how many numbers there are.
[tex]mean=\dfrac{a_1+a_2+a_3+...+a_n}{n}[/tex]
We have: 18, 16, x, 9, 12, 23 - six numbers (n = 6) and mean = 15.
Substitute:
[tex]\dfrac{18+16+x+9+12+23}{6}=15\\\\\dfrac{78+x}{6}=15\qquad\text{multiply both sides by 6}\\\\6\!\!\!\!\diagup\cdot\dfrac{78+x}{6\!\!\!\!\diagup}=(6)(15)\\\\78+x=90\qquad\text{subtract 78 from both sides}\\\\78-78+x=90-78\\\\x=12[/tex]
