how do you do input and output with equations,
Usually when people use the terms input and output, they mean pretty much the same thing as independent and dependent variable. Often, an equation will have the form:
y = some function involving x
The input is a number you put in to find the output. The output is what you would be calculating. A really simple example: you want to know how much money you'd have to spend total if you are getting some number of $10 t-shirts.
The number of t-shirts is the input, or independent variable, which we will call x. The total amount of money you are spending is then the output, or dependent variable (because it depends on the number of t-shirts), and we will call this y. The equation you would need to solve this problem for any number of t-shirts is:
y = 10x
You would put in (input) the number of t-shirts you are getting in place of x, and would come out with the total amount of money you'd need to spend (output).
Hope that helped :)