Gasté mi madre en ropa ayer cuando fuimos de compras.
a.

el más que

b.

menos que

c.

más como

This is a comparison of inequality. Comparisons of inequality just as mas que conveys the idea of more than or menos que conveys the idea of less than. These are used to point out that two things are not equal.

So the Less formula can be written as follows:

menos + adjective/adverb/noun + que

In this sentence we use a noun between menos and que. So:

Gasté menos que mi madre en ropa ayer cuando fuimos de compras

answer: c.

explanation: the answer is c