you can't solve this nor find the value of y because its not a full equation
The answer to your question
is 80%
Answer:

Step-by-step explanation:
The exponential decrease formula that we must use is:

Where A is the amount of thorium as a function of time
is the initial amount and k is the decrease rate
We know that initially there are 50 gr and that you decay 50% every 1.9 years.
So


We solve the equation for k





After 22.8 years the amount of thorium that exists is:


Solve:-
x + 67 = 83
Inverse operation.
83 - 67 = x
83 - 67 = 16
x = 16
Check:-
x + 67 = 83
x = 16
16 + 67 = ?
16 + 67 = 83
Correct!
x = 16
There are

possible pairs they can choose. Let

and

denote the integers that Sofia and Tess, respectively, choose, so that

denotes the integer pair.
The event that either

or

has 5 possible ways of occurring:

So the probability of this happening is

. You're interested in the complement, which means the answer is 95%.