Final answer:
The slope of the line in the given situation is 5.
Step-by-step explanation:
To represent the situation of needing customized ribbon for a Halloween costume, you can use the equation y = 5x + 10, where y represents the total feet of ribbon and x represents the number of minutes. The slope of the line in slope-intercept form is the coefficient of x, which in this case is 5.
Therefore, the slope of the line is 5.