You start by figuring out how fast a lap is so you do 4.5 (4 1/2 miles)/3 =1.5 minutes
Which means it takes her 1.5 minutes to do 1/4 mile so you times that by four to get how long it takes her to run a mile 4x1.5 =6
This means it takes her 6 minutes to run a mile To get this into miles per hour you divide 60 (because there’s 60 minutes in an hour) by 6 (her mile time) 60/6 =10