SOLUTION: Hi can anyone help me with these two? I have been on them since early this morning and can't seem to get it. Actualy, there are 8 problems, but if I can get these two going, I thi

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Question 172025: Hi can anyone help me with these two? I have been on them since early this morning and can't seem to get it. Actualy, there are 8 problems, but if I can get these two going, I think I can figure out the rest. I do appreciate any help you can give me.
Word problem:
The population of North America is growing rapidly. The equation that predicts this growth is -5.4x+y=372, where x is the number of years since 1980 and y is the population in millions of people. The population of South America is also growing rapidly. The equation that predicts this growth is -5.25x+y=242, where x is the number of years since 1980 and y is the population in millions of people.
1. According to these equations, what was the population of North America in 1980? In 2000? What will the estimated population be in 2010?
2. According to these equations, what was the population of South America in 1980? In 2000? What will the estimated population be in 2010?

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
(1)
If x is the number of years since 1980, then in 1980 x+=+0
Putting this into the equation for N. America,
-5.4%2A0+%2B+y+=+372
y+=+372
There were 372 million people in N. America in 1980
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In 2000, x+=+20
-5.4%2A20+%2B+y+=+372
-108+%2B+y+=+372
y+=+372+%2B+108
y+=+480
There were 480 million people in N. America in 2000
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In 2010, there will be
-5.4%2A30+%2B+y+=+372
y+=+372+%2B+162
y+=+534
There will be 534 million people in N. America in 2010
--------------
(2)
In S. America, in 1980
-5.25%2A0+%2B+y+=+242
y+=+242
There were 242 million people in S. America in 1980
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In 2000
-5.25%2A20+%2B+y+=+242
-105+%2B+y+=+242
y+=+347
There were 347 million people in S. America in 2000
--------------
In 2010,
-5.25%2A30+%2B+y+=+242
-157.5+%2B+y+=+242
y+=+399.5
There will be 399.5 million people in S. America in 2010