Let
x ------> number of guests
y ----> the total charge
Part a
we have that
the linear equation is
y=18x+200
Part b
the slope is m=18
that means------> $18 per person served
the y-intercept is b=200
that means ------> the initial charge by fee
Part c
For x=250 guests
substitute in the equation
y=18(250)+200
y=$4,700