Final answer:
Jamie spends 18 minutes jumping hurdles, which is calculated by taking 20% of the total 90-minute track practice time.
Step-by-step explanation:
To determine the amount of time Jamie spends jumping hurdles, we need to calculate 20% of the total track practice time. Jamie's track practice lasts 90 minutes, so we calculate 20% of 90 minutes as follows:
Time spent jumping hurdles = 20% of Total practice time
Time spent jumping hurdles = 0.20 × 90 minutes
Time spent jumping hurdles = 18 minutes
Therefore, Jamie spends 18 minutes jumping hurdles during the track practice.