A number is thrice the second number. The second number is also twice the third number. If the average of the three numbers is 18, find the numbers.

x - 1st numbery - 2nd numberz - 3rd number[tex]x=3y\\
y=2z\\
\frac{x+y+z}{3}=18\\\\
x=3y\\
z=\frac{y}{2}\\
x+y+z=54\\\\
3y+y+\frac{y}{2}=54\\
6y+2y+y=108\\
9y=108\\
y=12\\\\
z=\frac{12}{2}\\
z=6\\\\
x=3\cdot12\\
x=36\\\\
\boxed{36,12,6}[/tex]