If the measure of ðdcb = 100°, and ðdac = 20°, what is ðcab?

How do i do this? i don’t understand

Aretha wanted to gather data about the cost of local bowling leagues in her area. she plotted the data and determined that the average bowling league costs consist of a one-time registration fee and a monthly fee modeled by the equation y = 15x + 20. identify and interpret the y-intercept in this model. the y-intercept is 20. this is the cost per month. the y-intercept is 20. this is the cost of registration. the y-intercept is 15. this is the cost of registration. the y-intercept is 15. this is the cost per month.

Ineed to know the ordered pairs for this equation i need the answer quick because it’s a timed test