Write the algebric expression of the difference of'a' and 'b'

Kayla has a $500 budget for the school party.she paid $150 for the decorations.food will cost $5.50 per student. what inequality represents the number of students,s, that can attend the party?

Through non-collinear points there is exactly one plane.

What is the axis of symmetry of the function f(x)=-(x+ 9)(x-21)