In January 2008,the number of active my space users was 10 million fewer than double the number of active facebook users if the two social networking sites has a total 170 million users, how many people used each of the web sites?

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Answer 1 · 2018-01-22T22:07:32

See a solution process below:

Let's call the number of MySpace users: #s#

Let's call the number of Facebook users: #f#

We can then state the number of MySpace users in terms of Facebook users as:

#s = 2f - 10,000,000#

We also know from the problem:

#s + f = 170,000,000#

Substituting #2f - 10,000,000# for #s# and solving for #f# gives:

#2f - 10,000,000 + f = 170,000,000#

#2f + f - 10,000,000 = 170,000,000#

#3f - 10,000,000 = 170,000,000#

#3f - 10,000,000 + color(red)(10,000,000) = 170,000,000 + color(red)(10,000,000)#

#3f - 0 = 180,000,000#

#3f = 180,000,000#

#(3f)/color(red)(3) = (180,000,000)/color(red)(3)#

#f = 60,000,000#

Substituting this into the first equation and calculating #s# gives:

#s = (2 * 60,000,000) - 10,000,000#

#s = 120,000,000) - 10,000,000#

#s = 110,000,000#