3x+34×-40×=0

3 answers

add up your x's
3x+34x-40x is -3x
make that equal zero
-3x=0
then divide both sides by -3 to get x alone
x=-3
sorry,,,,wrong..can't divide by 0

did you mean
3x+34×-40=0
so who's dividing by zero?
0/-3 = 0
because 0 = 0 * -3

0*anything = 0

also, "x" is a variable name
"×" is the multiplication operator, usually typed as * online to avoid the confusion.
Just wondering why, since your keyboard has an "x" key, you switched to using the "×" symbol ...