You find out how much money Sonja had before she paid by taking the $30 she had left and adding it to the $12.50 she paid. $30.00-$12.50 = $42.50
Answer:
The percentage rate of decay per year is of 3.25%.
The function showing the mass of the sample remaining after t is 
Step-by-step explanation:
Equation for decay of substance:
The equation that models the amount of a decaying substance after t years is given by:

In which A(0) is the initial amount and r is the decay rate, as a decimal.
Every 21 years, its mass decreases by half.
This means that
. We use this to find r, the percentage rate of decay per year.



![\sqrt[21]{(1-r)^{21}} = \sqrt[21]{0.5}](https://tex.z-dn.net/?f=%5Csqrt%5B21%5D%7B%281-r%29%5E%7B21%7D%7D%20%3D%20%5Csqrt%5B21%5D%7B0.5%7D)



The percentage rate of decay per year is of 3.25%.
Given that the initial mass of a sample of Element X is 80 grams.
This means that 
The equation is:



The function showing the mass of the sample remaining after t is 
<span>Annie traveled 17 hours and Brian traveled 3 hours. 17+3=20. 3*5=15+2=17.</span>
Answer:
y = 1
x = -3
Step-by-step explanation:
9x + 2y = 3
-x - y = -12 (multiply second equation with 9)
9x + 2y = 3
-9x - 9y = - 108 (add these to up)
-7y = -105
y = 15 use this to find x
9x + 2y ➡ 9x + 30 = 3 ➡ 9x = -27 ➡ x = -3
4 is the greatest common factor of 32 and 44