Complex sentence: Around eighty percent of people are left hemispheric for speech and the remainder are right hemispheric: ninety percent of right handers are left hemispheric for speech, but only fifty percent of left handers are right hemispheric for speech (the remainder are left hemispheric).
Split into simpler sentences: Around eighty percent of people are left hemispheric for speech and the remainder right hemispheric. Ninety percent of right handers are left hemispheric for speech but only 50 percent of left handers are right hemispheric for speech (the remainder are left hemispheric).