SOLUTION: simplify: 9m-4m+8x-3x ????

Think of "m" as standing for "marbles" and "x" standing for
"xylophones".

Now the problem is

9 marbles - 4 marbles + 8 xylophones - 3 xylophones.

This could be stated:

Jack gave Jill 9 marbles.  So Jill has 9 marbles.

Then Jill gave Sally 4 marbles.  So Jill now has only 5 marbles.

Then Suzy gave Jill 8 xylophones.  So Jill now has 5 marbles and 
               8 xylophones.

Then Jill gave Hattie 3 xylophones. So Jill now has 5 marbles and
               5 xylophones. 

So Jill ended up with 5 marbles and 5 xylophones or

                5m + 5x
---------------

In short,  9m - 4m + 8x - 3x

means 9 m's minus 4 m's plus 8 x's - 3 x's

So that leaves 5 m's plus 5 x's or

                  5m + 5x

You just figure the number of m's and then the number of
x's.

Edwin