I think it means like explain what are variable is. Only if your finding a variable: explain how you got the answer to that variable. Hope I helped!
To answer the question above, I let x be the number of calendars sold. You may use any other letter as this is just for representation. The total income generated in selling calendars is calculated by multiplying the number of calendars with the price. That is,
total income = 5x
If we let total income be y, our equation is further simplified into,
y = 5x
Part A:5=2x^2-x^2+13
5=x^2+13
0=x^2+13-5
0=x^2+8
Part B:5=2x^3-x^3+13
5=x^3+13
0=x^3+13-5
0=x^3+8
