Meaning of よれ in Japanese

妹から便りがあった。手紙によれば目下元気だそうだ。
I heard from my sister. The letter says she is well now.

三人寄れば文殊の知恵って言うだろ。みんなで考えれば、いい案が浮かぶかもしれないよ。
Let's all think on this together and we might be able to come up with some good ideas. They say two heads are better than one.

予鈴だ。校門の辺りにいた生徒たちが一斉に足を速める。
It's the class bell. The pupils that had been around the school gate quickened their steps as one.