The amount of money alan earns as a plumber after x hours is modeled by the equation y=$25x + $50. what is the meaning of $25 in this model?

The $25 in the equation, y = $25x +$50 is just the rate of Alan as a plumber per hour. And regardless of the number of hours he could finish his job, there will always be an additional fee of $50. Likewise, the plumber has been given $50 before the project has started, or at the x = 0 hours: y = $25(0) + $50 = $50.