Question

Medical researchers have determined that for exercise to be beneficial, a person’s desirable heart rate, R, in beats per minute, can be approximated by the formulas

4072-01-02-03-00_files/i0230000.jpg for women
4072-01-02-03-00_files/i0230001.jpg for men,

where a represents the person’s age. If the desirable heart rate for a man is 135 beats per minute, how old is he?
a.
22.5 years old
b.
40 years old
c.
45 years old
d.
42.5 years old

Answer 1

You can drag the image here to post it

Answer 2

women's formula: 143 - 0.65a
men's formula: 165 - 0.75a

@dude would you like to take it from here?

Answer 3

We know that the patient is a man so we can use the second equation
\(R=165 - 0.75a\)
We know that the heart rate its 135 beats per minute so we can simply substitute it for R
\(135=165-0.75a\)