Asubstance decays so that the amount a of the substance left after t years is given by:
a = a 0 · (0.9) t ,
where a 0 is the original amount of the substance. what is the half-life (the amount of time that it takes to decay to half the original amount) of this substance rounded to the nearest tenth of a year?

Arectangular courtyard is 12 feet long and 8 feet wide. a tile is 2 feet long and 2 feet wide. how many tiles are needed to cover the courtyard?

Will mark brainliest, , and rate to only chrislaurencelleenzo is making a scale drawing of the rectangle below. ~imageenzo says that he can draw an enlarged rectangle that is 16 centimeters by 13 centimeters. which explains whether enzo is correct? enzo is correct because he used a factor of 2 to enlarge the rectangle. enzo is correct because he doubled one dimension and added the two lengths to get the other dimension. enzo is not correct because the enlarged rectangle should be 16 centimeters by 5 centimeters. enzo is not correct because he did not multiply the length and width by the same factor.

Which expression is equivalent to 5a/4 - b/8 ?