Introduction to More About Word Problems:  The word problems we
looked at in the previous section were obvious. They practically
shouted out, "Look! I'm a word problem and I'm talking about two
lines!'' Aside from their outbursts being needlessly loud and
distracting us from our cross-stitching, it's also a little
presumptuous of them to assume we care. Now we're going to get
more subtle, not to mention quieter. These problems are more
likely to whisper than shout, which is good news for our ears as
well as this monogrammed pillowcase we're working on.  When we
solve a system of two linear equations, we're using two pieces
of information (the two equations) to find two unknown
quantities (usually called x and y).  When a word problem
contains two quantities we don't know and gives us two pieces of
information about these quantities, we can write a system of
equations to describe the word problem. Then we can use that
system of equations to solve the problem.  There are three main
parts to solving one of these