Jenny ran for 3/4 of an hour . her brother ran for 1/2 that time . how long did her brother run
The brother ran for half the time that Jenny did.
Jenny ran for 3/4 hour, 1/2 of that is how long the brother ran
3/4 * 1/2 = 3/8 the brother ran for 3/8 of an hour.
OR Jenny ran for 3/4 hour = 45 minutes
1/2 of 45 minutes = 22.5 minutes the brother ran
depends on what form you are looking for in you answer