Bonjour Madame,
I have often read about the usage of "Penser à + (quelqu'un)"
But in the sentence from the lesson which reads-
"Nous pensons à faire nos devoirs. Nous y pensons"
Here I think the form "penser de + (quelquechose) should be used as the people are forming an opinion of something(doing their homework)
So consequently the phrase should be replaced by 'en'.
The same thought is for the very next sentence.
Pls guide and verify whether my thought is correct or not.
Merci beaucoup.