To find the area of triangle ABC with vertices at A (0,3), B (10,6), and C (6,3), we can use the formula for the area of a triangle given by coordinates. The formula is:
\[ \text{Area} = \frac{1}{2} \left| x_1(y_2 - y_3) + x_2(y_3 - y_1) + x_3(y_1 - y_2) \right| \]
Substituting the coordinates into the formula:
- \( (x_1, y_1) = (0, 3) \)
- \( (x_2, y_2) = (10, 6) \)
- \( (x_3, y_3) = (6, 3) \)
We calculate as follows:
\[ \text{Area} = \frac{1}{2} \left| 0(6 - 3) + 10(3 - 3) + 6(3 - 6) \right| \]
This simplifies to:
\[ = \frac{1}{2} \left| 0 + 0 + 6(-3) \right| = \frac{1}{2} \left| -18 \right| = \frac{18}{2} = 9 \]
Therefore, the area of triangle ABC is 9 square units. This calculation confirms that the answer is indeed 9.