Question 995387
y, the dance cost, depends on x number of students.
{{{y=b*x+a}}}
The variables are being used differently from what is typically used in discussing slope-intercept form.  HERE,  "b" is the slope, and "a" is the vertical axis intercept.  Your points are still used in the regular form of  (x,y).


Once that is well understood, then form these equations for a system:
{{{system(b*50+a=1400,b*100+a=2600)}}}
Observe how this uses the points given,  (50,1400) and (100,2600).


You can most comfortably use the Elimination Method if you want to solve for a and b.