PLSS Help guys or girls lol i need help

The? half-life of a radioactive substance is 20 years. if you start with some amount of this? substance, what fraction will remain in 120 ? years

An account with a $250 balance accrues 2% annually. if no deposits or withdrawals are made, which graph can be used to determine approximately how many years will it take for the balance to be $282? it's e2020 ni️️as

Vanessa earns a base salary of $400.00 every week with an additional5% commission on everything she sells. vanessa sold $1650.00 worth of items last week.