That equation could change if voters turn on the Republicans in Congress.

"When we talk about age-appropriate clothing, the equation has changed dramatically," he said.

That equation changed, and a number of new companies entered the market.

The equation might change if it became clear that breast-feeding could protect babies from serious illnesses later in life.

Either way, the whole equation will have changed, quite likely for the better.

That equation is constantly changing, of course, because news develops in unforeseen ways.

But by 1891 the equation of power had changed.

Under the Clinton Administration's sweeping health care proposal, that equation would dramatically change.

But when the President decided he must act, the equation changed.

In fact, they'd better start ramping up their efforts, fight hard now, before that equation changed.