Answer:
x = 9
Step-by-step explanation:
1/2(6x - 10) + 10 = 5x - 13
3x - 5 + 10 = 5x - 13
3x + 5 = 5x - 13
3x + 18 = 5x
18 = 2x
x = 9
Answer:
y=5(x-2)+3 or y= 5x+7
Step-by-step explanation:
<span># of books = 4 ; original cost = 4*9=36; savings = 0.10*36= 3.60
</span>
<span># of books = 2 ;original cost = 2*20=40; savings = 0.20*40= 8.00
</span>
<span>Percent savings:
original total cost=$76
Total savings = $11.60
Percent savings: 11.60/76 = 0.1526..= 15.26%</span>
If 
is the amount of strontium-90 present in the area in year 
, and it decays at a rate of 2.5% per year, then
Let 
be the starting amount immediately after the nuclear reactor explodes. Then
or simply
So that after 50 years, the amount of strontium-90 that remains is approximately
or about 28% of the original amount.
We can confirm this another way; recall the exponential decay formula,
where is measured in years. We're told that 2.5% of the starting amount 
decays after 1 year, so that
Then after 50 years, we have
