Answer:
I
1. Cristina es <em>menos </em>talentosa <em>que </em>Andrés.
2. Pablo es <em>más </em>rápido <em>que </em>Adrian.
***
...mejor que... ----> ...<em>better than...</em>
...peor que... ----> <em>...worse than...</em>
...mayor que... ----> <em>...older than...</em>
...menor que... ----> <em>...younger than...</em>
3. Ustedes son todos menores que yo.
II
1. Cristina corre <em>más rápido</em> <em>que </em>Andrés.
2. Mariela estudia <em>más horas que </em>Felipe.
3. Pablo canta <em>mejor que </em>yo.
Explanation:
I
Comparison of adjectives.
1. In order to express that someone possesses <em>less </em>quality <em>than</em> the other, we use <em>menos. </em>This word has one single form (for both genders and both numbers) because it defines <em>the adjective </em>it stands by: <em>menos </em>talentosa. The word <em>que </em>is <em>than </em>in English - less talented than : <em>menos </em>talentosa <em>que</em>.
2. When we want to illustrate someone or something as having <em>more </em>quality, we use <em>más</em>. It precedes the adjective and attributes to it, as well as the noun described by the adjective, <em>more quality. </em>But when comparing one's quality to the quality of the other, we mustn't forget <em>que, </em>meaning than - faster than<em> </em>: <em>más </em>rápido <em>que.</em>
***
There are, however, some adjectives that have an irregular comparison. Those are:
- bueno/buena ---> mejor
- malo/mala ---> peor
- viejo/vieja ---> mayor
- joven ---> menor
These forms change in plural (mejor-es/peor-es/mayor-es/menor-es). Not all of these are necessarily <em>irregular</em> (read under the number 3) but the pair <em>bueno/malo</em> are the common irregular adjectives we know are irregular in English, too.
3. When it comes to age, it would be impolite to call somebody <em>más viejo. </em>This is not incorrect but rather <em>inappropriate</em>. Same goes for <em>más joven. </em>The person we are younger <em>then </em>could feel insulted. That is why in the third sentence we use <em>menor </em>and in plural (ustedes).
II
Other comparisons.
1. In this case we compare the running of both subjects. This implies that we are comparing adverbs (which describe actions/verbs). The process is the same as with adjectives. We use <em>más </em>when the quality of the action is <em>better</em>, and we use <em>menos </em>when the action is <em>worse. </em>These words describe adverb so they should be <em>in front of </em>them: <em>más </em>rápido.
2. This time we are comparing the quantity of something, more precisely, the quantity of hours. And if we are comparing the quantity of something, it means that <em>nouns</em> are in comparison. But the rules remain the same: <em>más </em>is when there is more of something, <em>menos </em>when there is less: <em>más </em>horas.
3. Here again we should compare the quality of an action: <em>to sing</em>. But here again we face <em>an</em> <em>exception</em>: <em>well </em>has an irregular comparison (again just as in English) and we must remember that. We cannot say <em>cantar más bien. </em>The comparative of <em>bien </em>is the same as for <em>bueno</em>: cantar <em>mejor</em>.
