The image contains a problem related to geometry, specifically involving a triangle and some calculations. Below is a summary of the content:

Problem Description:

1. A triangle $\triangle ABC$ is situated on the coordinate plane with the following details:

   • $A$ is the origin $(0,0)$.
   • $B$ is at $(18,0)$, meaning it's on the x-axis.
   • $C$ is a point such that its y-coordinate $y$ is 15.

2. There are several questions regarding the properties of this triangle:

   1. Calculate the length of $AB$.
   2. Calculate the length of $BC$ using the given coordinates.
   3. Determine the slope of the line $AC$ if point $C$ has a certain x-coordinate.
   4. Find the equation of the line passing through point $A$ and perpendicular to $BC$.
   5. Determine the area of $\triangle ABC$.

Would you like a detailed step-by-step solution to each of these problems, or do you have specific questions about any part of the problem?

Here are 5 related questions you might consider next:

1. How do you find the coordinates of a point $C$ in a triangle when given specific conditions?
2. What is the formula to calculate the distance between two points in a coordinate plane?
3. How can you determine if a line is perpendicular to another in the coordinate plane?
4. How do you calculate the area of a triangle given the coordinates of its vertices?
5. What is the relationship between the slope of a line and the angle it makes with the x-axis?

Tip: When solving problems involving coordinates, always ensure the units are consistent and double-check your calculations for accuracy.