84,600,600 write each number in scientific notation i have a dew more questions but im stuck 12points

Molly shared a spool of ribbon with 12 people. each person received 3 feet of ribbon. which equation can she use to find r, the number of feet of ribbon that her spool originally had?

The base of a rectangular pyramid is 13 inches long and 12 inches wide. the height of the pyramid is 8 inches. what is the volume of the pyramid

Devaughn's age is three times sydney's age. the sum of their ages is . what is sydney's age?