Answer:
A.
Step-by-step explanation:

Answer: 
This is the same as writing y = 650(0.907)^t
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Explanation:
Exponential equations can be of the form y = a*b^t
- a = initial amount
- b = growth or decay factor
In this case, we have
- a = 650 mg to start with
- b = 1 - 0.093 = 0.907 as the decay factor
If we had exponential growth, then we'd compute 1 + 0.093 instead.
Based on those values, we go from y = a*b^t to y = 650(0.907)^t which is the same as writing 
Other exponential forms are possible, but I think this form is the most intuitive. The 0.907 means that 90.7% of the sample remains after each year.
You have posted 2 separate questions here. Please, next time, separate them with a blank line:
<span>A circle has an area of 81 3.14 units . what is the diameter in terms of 3.14?
I'd prefer you write this as
"</span><span>A circle has an area of 81 pi units . what is the diameter in terms of pi?
Area of a circle = A = pi*r^2. Note that r= diameter / 2. Here, the area is 81 pi square units, or 9^2 * pi square units, which means that the radius is 9 units. The diameter is then 2(9 units) = 18 units.
Your second question, separated from the first, is:
"</span><span>a circle has an area of 81 Pi square units what is the diameter of the circle?"
</span><span>
Use the following formula or formulas: d = 2*r; A = pi*r^2; A = pi*(d/2)^2. Find r first, and then find d.
</span>
In the question there are numerous information's of immense importance already given. Let us write them down first
Distance traveled by bike = x km
Distance traveled by bus = y km
Total distance traveled by George and Carmen = 325 km
Then
x + y = 325
Another equation can be determined by
x - y = 75
x = y + 75
Now we will put the value of x in relation to y in the first equation.
x + y =325
y + 75 + y = 325
2y = 325 - 75
2y =250
y = 250/2
= 125 km
Now putting the value of y in equation given below, we get
x + y = 325
x + 125 = 325
x = 325 - 125
= 200 km
So the distance they biked is 200 km and the distance they traveled by bus is 125 km.
Answer:
In equation A, c = 7
In equation B, d = 5
Step-by-step explanation: