Element X is a radioactive isotope such that every 81 years, its mass decreases by half. Given that the initial mass of a sample of Element X is 1800 grams , how much of the element would remain after 28 years , to the nearest whole number?

The u-drive rent-a-truck company plans to spend $13 million on 320 new vehicles. each commercial van will cost $25 comma 000, each small truck $50 comma 000, and each large truck  $80 comma 000. past experience shows that they need twice as many vans as small trucks. how many of each type of vehicle can they buy?

The graph shows the distance kerri drives on a trip. what is kerri's speed?

Present age of man is 45 years, 5 years back his age was 4 times age of his son what is present age of his son?