Pls can some one help i need to know how to do this pls it's math?

Slope=[21951570]/[75-50]=25 , slope means meal charge per person , y=25x+c , 1570=25(50)+c , c=320=y-intercept which is fixed fee to rent hall , 5000=25x+320 , 4680=25x , x=187 guest can b invited