NET
18 A third of humanity was killed by these three plagues, that is, by the fire, the smoke, and the sulfur that came out of their mouths.
Darby
18 By these three plagues were the third part of men killed, by the fire and the smoke and the brimstone which goes out of their mouths.
KJV
18 By these three was the third part of men killed, by the fire, and by the smoke, and by the brimstone, which issued out of their mouths.