Day 3 > Lesson 7 Solving Two-Step Equations Practice 3 Marco is an operational manager of a concert venue and oversees crowd control. Thirty minutes before a concert, there were 800 people in the 2,000-seat auditorium where the concert was being held. Ten minutes before the concert, the auditorium was 75% full. The equation 0.75 = represents the situation, where p is the number of people who entered the auditorium during this time interval. Solve for p. people entered the auditorium. Practice 4 Maria is an airline pilot and flies planes all over the globe. The altitude a (in feet) of a plane t minutes after liftoff is given by a = 3400t + 600. How many minutes after liftoff is the plane at an altitude of 21,000 feet? The plane's altitude is 21,000 feet minutes after liftoff