Sometimes the noun form and the verb form of a word are the same. For example, the word “increase” can be a noun or a verb. The problem is that nouns and verbs are used differently. Here are some examples:
There was an increase in the unemployment rate. (noun)
The unemployment rate increased. (verb)
There is a lack of investment in hospitals. (noun)
Many hospitals lack the investment they need. (verb)
Companies should give men and women equal pay. (noun)
Companies should pay men and women equally. (verb)
It's the little words like "an increase in" that cause most problems for students. Examiners do notice these things, so it's worth getting them right.