"At Common Good we tried to stick to

85-15, so 85 percent of the food we grow are distributed within the community, then 15 percent we sell to local restaurants and a mobile farmers' market that comes once a week," she said.
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How do we read "85-15"?

Be sure to change "are" to "is" -- "85 percent" is treated as a singular subject.

85-15 = eighty-five fifteen