Need fast!

andrew measures the amount of a very unstable substance to be 100 moles. the half-life of this
substance is 3 days (after 3 days, half is gone).
write an exponential function that models this situation where y is the amount of substance
and x is time in days.

3

step-by-step explanation:

5=812a+9+3

step 1: simplify both sides of the equation.

5=812a+9+3

5=(812a)+(9+3)(combine like terms)

5=812a+12

5=812a+12

step 2: flip the equation.

812a+12=5

step 3: subtract 12 from both sides.

812a+12−12=5−12

812a=−7

step 4: divide both sides by 812.

812a /812 = -7/812

a= -1/116

so the answer is

a=   -1/116