Calculating Target Heart Rate - the formula

I have to be truthful. I seem to have been born with a fuzzy math gene and tend to stay away from math problems. I did this calculation last week for the first time in my online fitness class at BSU. I have seen the formula before, but have always taken the lazy path of letting my gadgets do the math work for me. So basically I let the Garmin do the work and take its word on it.

Here is the Kervorven (sp??) formula for calulating Target Heart Rate (or THR):
First palpate your pulse for 60 seconds while resting and calm. This is your Resting Heart Rate ( or RHR).
Then take:
220 - (your age) = estimated Maximum Heart Rate (or MHR)
MHR - RHR = Heart Rate Reserve (or HRR)
HRR x 0.60 + RHR = lower THR
HRR x 0.80 + RHR = higher THR

Kinda makes you wish you had paid better attention in that freshman Algebra class eh?