Step b is wrong. The slope is the change in y over the change in x.
Step b should be (18- 8)/( 10-6)
= 10/4
= 5/2
The answer is just do easy subtraction 3/4
-3/2
slope = rise/run
We can use the two points to calculate rise (y value change) and run (x value change)
slope = (-6)/4 = -3/2
In 4 seconds, number of beats = 28
In 1 sec., it is = 28/4 = 7
Now, In 30 seconds, it would be: 30 * 7 = 210
In short, Your Answer would be: 210 beats
Hope this helps!
