What is 21/36 in simplest form and in decimal form?

Which is a reasonable estimate of the amount of water in a small, inflatable pool used by children?

Can someone check if i did this correct. it’s number 4 if you’re wondering.

In 1995 america online had about 3000000 users over the next decade users are expected to increase from a few million to the tens of millions suppose the number of users increased by 150% by the year 2000 how many users will there be in the year 2000