Element X is a radioactive isotope such that every 25 years, its mass decreases by half. Given that the initial mass of a sample of Element X is 90 grams, how long
would it be until the mass of the sample reached 55 grams, to the nearest tenth of a
year?

Based on what i know about mean, this doesn't add up.

You decide instead to take the train there. the train will take 135 minutes. convert this into hours and minutes.

14 pointslet x be the seats in the small van and y the seats in the large van. how many seats does the large van have? a company uses two vans to transport worker from a free parking lot to the workplace between 7: 00 and 9: 00a.m. one van has 9 more seats than the other. the smaller van makes two trips every morning while the larger one makes only one trip. the two vans can transport 69 people, maximum.how many seats does the larger van have?