Answer: 51 years
Step-by-step explanation:
Given : During exercise, the recommended maximum heart rate in beats per minute is modeled by the formula :
[tex]M = 176 -0.8A[/tex] , where M is the maximum heart rate and A is the person’s age.
To solve  the formula for A , add 0.8A and subtract M on both sides , we get
[tex]0.8A=176M[/tex]
Divide 0.8 on both sides , we get
[tex]A=\dfrac{176-M}{0.8}=220-1.25M[/tex]
i.e. Formula for A : [tex]A=220-1.25M[/tex]
Put M= Â 135, we get
[tex]A=220-1.25(135)=51.25\approx51\text{ years}[/tex]
Hence, at the age of 51 years you would have a recommended maximum heart rate in beats per minute of 135.
