You participate in a dance-a-thon fundraiser. after your parents pledge $15.50 and your neighbor pledges $8.75, you have $66.55. write and solve an equation to find how much money x (in dollars) you had before your parents and neighbor pledged.

International calls require the use of a country code. many country codes a 3-digit numbers. country codes do not begin with a 0 or 1. there are no restrictions on the second and third digits. how many different 3-digit country codes are possible?

Hurry if the population of of an ant hill doubles every 10 days and there are currently 100 ants living in the ant hill what will the ant population be in 20 days

Use sigma notation to represent the following series for 9 terms.