If i have one output value and two input values i need to enter on the float line in c# how would i do that?

If i have one output value and two input values i need to enter on the
float line in c# how would i do that?

If my output value is Miles Per Gallon and my input values are Miles
traveled and Gallons of Gas Used how would i enter that after inputting
float?
Please help, my assignment is due tonight and i am pulling my hair out
trying to figure this out.