Answer:
1. No es cierto que las matemáticas sean muy difíciles.
2. El presidente no niega que el problema del cambio climático sea bastante complicado.
3. Ana duda que él vaya a terminar el trabajo a tiempo.
4. Mis amigos están seguros de que esa película es excelente.
5. No cabe duda de que el Español se usa más y más cada día.
6. No es seguro que Lourdes y yo podamos ir a ayudarte esta tarde.
7. El maestro no cree que Marcos escriba muy bien en francés.
8. No es verdad que Pedro y Virginia nunca coman carne.
Explanation:
The exercise aims for you to practice disagreements in Spanish which are made using a negation phrase like those that were in parentheses and changing the verb to the subjunctive mode. Notice that sentences 4 and 5 are not making a disagreement or a doubt so therefore the verb didn't change to subjunctive mode.
Here are some other phrases to mean disagreement:
No es probable/ It is not probable
Es poco probable / It is barely probable
Here is the translation of the complete sentences:
1. It is not true that mathematics are very difficult.
2. The president does not deny that the problem of climate change is quite complicated.
3. Ana doubts that he will finish the work on time.
4. My friends are sure that this movie is excellent.
5. There is no doubt that Spanish is used more and more every day.
6. It is not certain that Lourdes and I can go to help you this afternoon.
7. The teacher does not believe that Marcos writes very well in French.
8. It is not true that Peter and Virginia never eat meat.