An equation is a mathematical statement such that the expression
on the left side of the equals sign (=) has the same value as
the expression on the right side. An example of an equation is
200 + (- 600) = - 400. One of the terms in an equation may not
be know and needs to be determined. Often this unknown term is
represented by a letter such as x. (e.g. 200 + x = - 400). The
solution of an equation is finding the value of the unknown x.
To find the value of x we can use the subtraction property of
equations which says: The two sides of an equation remain equal
if the same number is subtracted from each side. We may also use
the addition property of equations which says: The two sides of
an equation remain equal if the same number is added to each
side. - 500 + x = 400 - 500 + x + 500 = 400 + 500 0 + x = 900 x
= 900 Check the answer by substituting the answer (900) back
into the equation. - 500 + 900 = 400