Trey runs 2.1 miles, five days a week. How many miles does he run in 2 weeks?

Answer 1

In a week, Trey runs 2.1 miles/day x 5 days/week = <<2.1*5=10.5>>10.5 miles.
Therefore, Trey runs 10.5 miles/week x 2 weeks = <<10.5*2=21>>21 miles in 2 weeks. Answer: \boxed{21}.