Since the word "invention" begins with a vowel sound /ɪnˈvɛnʃn/, we should use the indefinite article "an". As for "interested": the adjectives that end with "-ed" describe some sort of condition, feeling of either thing or human, temporary in general; the adjectives with "-ing" describe some kind of quality, generally permanent. Therefore, we should use "interesting". The rest is contextual.
Cinco de mayo makes america unique because it celebrates all the Mexicans, another celebration that takes place in america is Hanukkah. these celebrations teach us that there is people that are different and have different beliefs but it’s okay because in the end we always have to be together as one . (hope it helped)
