The best way to be sure that experimental results are vaild

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)

sodium i think the chemical element of atomic number 11, a soft silver-white reactive metal of the alkali metal group.