Explanation:
a function with a single input variable x is usually defined like
y = f(x) = expression in x
to "solve" it means either to have a value for x and then calculate y.
or to have a value for y and find the corresponding value for x, so that f(x) = y. this usually involves finding and using the inverse function of f(x).
the details depend on the functions and operations used in the function expression.