It's "rojas".
Since "bicicletas" is plural, with a feminine ending, you pick "rojas", with it's plural, feminine ending.
Answer:
ether is an especially good solvent for the formation of Grignard reagents because ethers are non-acidic (aprotic). Water or alcohols would protonate and thus destroy the Grignard reagent, because the Grignard carbon is highly nucleophilic. This would form a hydrocarbon.
2/5- 1/4= (2 × 4) - (1 × 5)5 × 4= 3/20
