<PRE><B>Question 831056</B>
Your given equation has three terms:
-31xm;
-2;
618.


The grouping symbols around -31xm emphasise the grouped factors as a separate number from other numbers and symbols in the equation.  


The variable term is  -31xm.  A person may want to solve for one or other of the variables contained in this term.  Objective is to isolate the variable term, and finally one of the variables.


The left member contains -2.
We maintain equality between left and right members if we ADD THE ADDITIVE INVERSE OF -2 TO BOTH THE LEFT AND RIGHT MEMBERS.
-31xm+(-2)+2=618+2  ----- removing parentheses from -31xm causes no trouble; putting parentheses around -2 both emphasises that number and on this site will help with rendering.
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-31xm+0=618+2 ----- Property and meaning of ADDITIVE INVERSE.</PRE>