Posted by HELP on .
At football practice, players do a 20minute warmup before starting their practice drills. After the practice drills, they do a 10minute cooldown. The expression 20+d+10 describes the length of practice, where d is the number of minutes the practice drills last. How long, in minutes, does practice last if 30 minutes are spent on practice drills.

Mathematics 
Peter,
Plug in d. D = the number of minutes the practice drills last
"30 minutes are spent on practice drills."
20 + 30 + 10 = 60 minutes.