You can build an expression tree which contains a "less than" numeric comparison using Expression.LessThanOrEqual method. For example, you have the following code.
bool value = 31 <= 31;
Console.WriteLine(value);
Here is the code that is required to build the same functionality using expression tree.
Expression expr = Expression.LessThanOrEqual(
Expression.Constant(31),
Expression.Constant(31)
);
Console.WriteLine(Expression.Lambda<Func<bool>>(expr).Compile()());