Need help i dont understand

The size of a certain cell is 2.5*10^-9m. another cell is 1.5*10^3 times larger. how large is the larger cell in scientific notation?

Nick and nora are married and have three children in college. they have an adjusted gross income of 47,400. if their standard deduction is 12,600 itemized deductions are 14,200 and they get an exemption of 4000 for each adult and each dependent what is their taxable income

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