Those are two idioms. Braç a braç means arm in arm, to be in good terms. Colze a colze means side by side. But there is a catch, because they wrote colze amb colze (note the preposition), a word-by-word translation of a Spanish idiom, codo con codo, which means the same. IMO, this exercise tries to advise the learners about the dangers of word-by-word translation of idioms and structures from Spanish, a language from which Catalan gets too much contamination due to the diglossia.