At the end of a certain year, the four companies with the largest number of home internet users in the united states were microsoft, time warner, yahoo, and google, with a combined audience of 284 million users. taking x to be the microsoft audience in millions, y the time warner audience in millions, z the yahoo audience in millions, and u the google audience in millions, it was observed that

z − u = 3(x − y) + 8
x + y = 50 + z + u
and x − y + z − u = 44.