Equations as a balance

0:00How do we solve 3x plus 2 equals 14?

0:04An equation is like a balance, with equal amounts on both sides.

0:09The left side holds three x boxes and two blocks.

0:14The right side holds fourteen blocks.

0:17We want to find how many blocks one x box is worth.

0:21First, take the two blocks off the left side.

0:25Now the sides are not equal, so the scale tips.

0:29Take two blocks off the right side too, and the scale is level again.

0:34Now three x boxes balance twelve blocks, so 3x equals 12.

0:40Next, split each side into three equal groups.

0:45Each x box matches a group of four blocks.

0:49Keep one group on each side, and one x box balances four blocks.

0:54So x equals 4.

0:57Check it: 3 times 4 plus 2 is 14, the same as the right side.

1:04Whatever you do to one side of an equation, do the same to the other side.