Haley held <<8=8>>8 marshmallows.
Michael held 3 times Haley's, so he held 8 x 3 = <<3*8=24>>24 marshmallows
Brandon held half as many marshmallows as Michael, so he held 24 / 2 = <<24/2=12>>12 marshmallows
Together, they held 8 + 24 + 12 = <<8+24+12=44>>44 marshmallows.
#### 44