You would 'b' be in '-20= -8(4)+b'

An unknown number of kids and buses are getting assigned. when assigning 4 kids to each bus, there are 2 kids that aren't placed in a bus. when assigning 8 kids to each bus, there are 2 empty buses. how many total kids are there?

Can someone me out here and the tell me the greatest common factor

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