Algebra 2 (1st Edition)

$x=3$
$4x+9=21$ First we move the 9 to the other side of the equation to isolate the "x" on one side. Moving the 9 will cause it to become negative. $4x=21-9$ $4x=12$ Then we will divide the equation by 4 so we could get the value of the single "x" $4x=12 /:4$ $\frac{4}{4}x=\frac{12}{4}$ $x=3$