The half-life of iodine-123 is about 13 hours. You begin with 50 grams of iodine-123.

Write an equation that gives the amount of iodine-123 remaining after t-hours.

It says that the equation ends up being I(t) = 50(.948)^t. In the middle of finding the final equation there is a part that goes like this: when t = 0 I(t) = 25 so 25 = 50B^13 then it goes into the final equation I(t) = 50(.948)^t.

My question is how do you get .948 from B?