Kelly's mom timed her as she swam a three lap race in 1minute 43secinds. Her swimming coach timed kelly only on her last two laps describe how kelly might calcite how long it took her to swim the first lap using the information from her mom and coach

See explanation below

Step-by-step explanation:

Lap 1 + Lap 2 + Lap 3 = 1 min 43 seconds

Lap 2 + Lap 3 = timed by coach

Hence,

Lap 1 + "timed by coach" = 1 min 43 seconds

Lap 1 = 1 min 43 seconds - "timed by coach".

So, Kelly can subtract the time taken on last 2 laps (from coach) from 1 minutes and 43 seconds