Answer:
watch the video
Step-by-step explanation:
I would make both denominators the same, and the lowest one that works is 18. So I'd make 1/9 into 2/18, and 1/6 into 3/18. They already used these times so combine them to make 5/18 then subtract that from the total time they had (18/18) and you would get 13/18 they spent playing music.
From all those aforementioned, the true statement is: Thanh’s grade is 2.5 standard deviations below the mean of the test grades.
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:

Hope that helped I use this when I'm doing math. It's called cymath it explain how they got the answer.