The watch costed $400 before the discount.
76 * 100 = 7,600
7,600 / 19 = 400
I believe the answer is A! If not I’m so sorry but I hope you pass!
60/25 = 12/Y
cross multiply and divide
25 x 12 = 300
300 / 60 = 5
Y = 5 boxes
Answer:
a)
, b)
, c)
, d) 
Step-by-step explanation:
a) Let assume an initial mass m decaying at a constant rate k throughout time, the differential equation is:

b) The general solution is found after separating variables and integrating each sides:

Where
is the time constant and 
c) The time constant is:


The particular solution of the differential equation is:

d) The amount of radium after 300 years is:
