y and x equations

[esteemed_longevity]

can someone explain how the y and x equations can produce a straight line?

[Kevin]

I believe you are talking about equations that come in the form of y = mx + b. If that is the case, when you plug in a number as x, the output would be y. Since m and b don't change, the output would change at constant amounts producing a line that either goes up or goes down. Hope that makes it clear!