Answer:
102 ≤ heart rate ≤ 183.6
Step-by-step explanation:
... lower limit ≤ heart rate ≤ upper limit
Put 16 where "a" is and do the arithmetic.
... lower limit = 0.5(220 -16) = 102
... upper limit = 0.9(220 -16) = 183.6
Then the inequality is ...
... 102 ≤ heart rate ≤ 183.6
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Comment on the problem
There is nothing to "solve" here. One only needs to evaluate the limits.
