If you subtract 426 from 913 how many times would you need to regroup? and how can you tell?

Acredit union pays 5% annual interest, compounded daily, on savings deposits. find the value after one year of $500 deposited in this account. $525.64 $25.64 $20.40 $520.40

According to the general equation for conditional probability if p(anb)=3/7 and p(b)=7/8 what is p(a i b)

Pls the last one and it has to be like number 6