My answer got deleted for some reason, so here we go again. To convert a number to a percent, you multiply the number by 100. So if you had the number 2.4, you would multiply it by 100 to get 240%. After multiplying it by 100, simply add a percent sign, and you're done!
Multiply 3 * 1 1/2 to find how many miles she runs per hour
1 1/2 * 3
3/2 * 3
9/2
4 1/2 She will run 4 1/2 or 4.5 miles per hour.