Answer
a. $95$ beats per minute
b. $114$ beats per minute
Work Step by Step
$a.$
Substitute 30 for a into the formula for the Lower limit:
$H=\displaystyle \frac{1}{2}(220-30)=\frac{1}{2}\cdot 190=\frac{190\div 2}{2\div 2}=\frac{95}{1}$
$=95$ beats per minute
$b,$
Substitute 30 for a into the formula for the Upper limit:
$H=\displaystyle \frac{3}{5}(220-30)=\frac{3}{5}\cdot 190=\frac{3\cdot 190\div 5}{5\div 5}=\frac{3\cdot 38}{1}$
$=114$ beats per minute
