Katie got three division problems wrong.

凯蒂答错了三道除法题。

For example, instead of practicing 20 consecutive multiplication problems, mix it up with addition, subtraction, and division problems.

例如，与其练习 20 个连续的乘法题，不如将其与加法、减法和除法题混合起来。

But we can also use the Kw and the hydronium ion concentration to do a very simple division problem and find the hydroxide concentration.

当氢离子浓度上升时pH值会降低举个例子，一种弱酸比方说醋酸，被加到水中时。