Question

fix the two plural or possessive errors.
bike - sharing programs are cropping up throughout the united states.
as of summer 2014, more than twenty - one thousand bicycles were available
in approximately thirty - six of the nations urban areas.

Explanation:

1. For "bicycles'": The word "bicycles" here is a plural noun referring to the bikes available, and we don't need the possessive form (the apostrophe) because we are not showing ownership. So we should remove the apostrophe to make it "bicycles".
2. For "nations": To show that the urban areas belong to the nation (or nations, but in context, likely "nation's" or "nations'". Since it's "thirty - six of the...", it's more likely "nations'" to show that the urban areas are of the nations. So we change "nations" to "nations'".

Answer:

1. Change "bicycles'" to "bicycles".
2. Change "nations" to "nations'".