Expert: Lynn Houston - 1/27/2010

Question
Helping my son with homework, he forgot his math book. How would I explain to him how to find this answer. 4/9 x ____ = -4 I got the correct answer of -9 but am missing the simple way to explain it to him.  Thanks for all your help.

Answer
Treat the "space" as a variable, lets say z and then "undo" everything done to z (this is assuming that the x in your equation means multiplication).  And, everything you do to one side of the = sign you have to do to the other.  

4/9(z) = -4 Multiply both sides by 9/4 (that will cancel out the fraction and just leave z)
4/9(9/4)z = -4(9/4)  do the math (ie multiply)
z = -9

Hope this makes sense.