What number is 250 decreased by 14%

What is the definition of exponential decay?

A33 gram sample of a substance that's used to detect explosives has a k-value of 0.1473. n = noekt no = initial mass (at time t = 0) n = mass at time t k = a positive constant that depends on the substance itself and on the units used to measure time t = time, in days

At your job you're paid $50 per week plus $3 per sale at least how many saled do you need to make in order to have over $250