Just reverse search this on google
Answer:
1 
Step-by-step explanation:
Note there is a common ratio between consecutive terms, that is
10 ÷ 20 = 5 ÷ 10 = 2
÷ 5 = 
Thus to obtain the next term in the sequence multiply the previous term by 
2
×
= 1 
Im not for sure if i did this right but my calculator says that its 420.
hope i helped.
I really don’t know maybe you’ll have summer school that’s what we have to do if we fail an online course we have to go to summer school.