What is the missing number 7/18=21/

Movie $5.50 soda $1.75 popcorn $2.25 candy bar $1.10 jeffrey left home with $20 in his wallet. he had a quick lunch that cost $8.47 and went to the movie theater. which of these activities can jeffrey do? a) go to movie and take two friends b) go to movie and have a soda, a popcorn and a candy bar c) go to movie, take a friend, and have a popcorn to share d) go to a movie, have 2 popcorns, 2 sodas, and 2 candy bars eliminate

Need on this geometry question. explain how you did it.

The two square pyramids are similar. find the total volume of both pyramids if the ratio of their surface areas is 9/16