The sum of three consecutive multiples of $3$ is $72$. What is the largest number among them?

Let the three consecutive multiples of $3$ be $x$, $x+3$, and $x+6$.
Given that their sum is $72$:

$$x+(x+3)+(x+6)=72$$

$$3x+9=72$$

$$3x=72-9$$

$$3x=63$$

$$x=\frac{63}{3}=21$$

The three consecutive multiples are $21$, $24$, and $27$.
The largest number among them is $27$.