Do not use the ipmon -a syntax if the ipmon daemon is still running. Normally, the daemon is automatically started during system boot. Issuing the ipmon -a command also opens another copy of ipmon. In such a case, both copies read the same log information, and only one gets a particular log message.
Substitution method is a method of solving a system of equations wherein one of the equations is solved for one variable in terms of the other variables.
It means to solve for the x and y values that make both equations true, using the elimination method. Elimination is just one way of solving (substitution is another way) and is sometimes called linear combination. Here's how: