I know that the answer is 3 because 1+2 is 3
Answer:
The starting position of the runner.
Explanation:
When you look at the graph, you can see that the first point on the graph is twenty on the y-axis.
The runner starts at twenty, and ends at thirty.
Therefore, the runner starts at twenty on the y-axis, so it's the starting position of the runner.
The tension in the string and the acceleration must be equal for both masses. (See the free body diagrams)
It is called a dotted half note.