儿童商店里,15元可以买5个文具盒,买3个这样的文具盒要多少钱?列式为____。
①15×3 ②15÷5×3 ③15÷3×5
(○代表神经元细胞体,<代表神经末梢,且ab=bc、ac=de)
His teacher isn't happy his explanation.