Answer:
<h3><em>HOPE IT'S HELPS </em><em>YOU.</em><em>.</em><em>.</em><em>.</em></h3>
I think that you round to 9.80 seconds. Pardon me, I didn't understand the problem well
7-5x-(3+5x)
7-5x-3-5x
4-10x
This is my answer☺
1.Do the parenthesis first
2.Combine the like term
I'm not sure if that's what you mean, but I assume you might want to know how long did it take to make one lap if someone did 21 laps in 7 minutes.
If so, just divide 7 by 21:
7 ÷ 21 = 0.3333333... (repeating decimal) or 1/3 as a fraction.
It means that one lap took 1/3 of a minute (20 seconds).
If that's not what you meant, please specify the question :)