Trey's hit roll: 11 + 15/2 = 19
Cactifake's dodge roll: 11 + 10/2 = 16
Trey's Damage Rolls: 2 + 3 + 17/2 + 6 = 20 (2d6 for Fira, +1d6 because fire spell)
Cactifake's HP: 0
Trey's MP: 4/10