An inter-agency task force has representatives from 3 different agencies. Half of the task force members represent agency A, one-third represent agency B and three represent agency C. How many people are on the task force?

Let $T$ be the total number of people on the task force.

• Agency A: Half of the task force members, which is $\frac{1}{2}T$.
• Agency B: One-third of the task force members, which is $\frac{1}{3}T$.
• Agency C: Three members, which is 3.

The sum of members from all agencies must equal the total number of members:

Find a common denominator for $\frac{1}{2}$ and $\frac{1}{3}$, which is 6.

Subtract $\frac{5}{6}T$ from both sides of the equation:

Multiply both sides by 6:

The total number of people on the task force is 18. This corresponds to option d.

The final answer is $\text{d. 18}$.