You can look for the number 16 on the x-axis. (bottom line) and put a finger there. Then, look for 19 on the y -axis (left line) and put a finger there. Trace your left finger to the right and your right hand up until they meet. That is (16,19)
I assume by starting value, you mean y-intercept. The y-intercept is 15
To find this, we need to use slope intercept form and the given information to find it.
y = mx + b ----> plug in the known values
9 = -3/4(8) + b
9 = -6 + b
15 = b
Therefore, the starting value is 15.