X miles per hour - <span> speed of the boat in still water
(x - 2) - speed up the river
(x + 2) - speed down the river
</span>

=

30 * (x + 2) = 38 * (x - 2)
30x + 60 = 38x - 76
- 8x = - 136
x =
17 miles per hour - <span>
the speed of the boat in still water.</span>
Step-by-step explanation:
You have miscopied the second equation as it contains a third variable B when there isn't a B in the answers.
Please correct it for assistance
The original air present after 8 breaths will be equal to 179.81 ml.
<h3>What is an equation?</h3>
The equation in mathematics is the relationship between the variables and the number and establishes the relationship between the two or more variables.
It is given in the question that:-
During normal breathing, about 12% of the air in the lungs is replaced after one breath
If the initial amount of air in the lungs is 500 mL
how much of the original air is present after 8 breaths?
The calculation for the eduction of the air will be done by the following equation:-

=179.88 ml
Hence original air present after 8 breaths will be equal to 179.81 ml.
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Answer:
20
Step-by-step explanation: