Which matrix equation has the solution

Element x decays radioactively with a half life of 8 minutes. if there are 450 grams of element x, how long, to the nearest tenth of a minute, would it take the element to decay to 37 grams?

What is the measure of ac? 5 units 13 units 26 units 39 units 3x- 2b 6x + 9

Identify the initial amount a and the growth factor b in the exponential function. a(x)=680*4.3^x