You can build an expression tree which contains a "greater than" numeric comparison using Expression.GreaterThan method. For example, you have the following code.
bool value = 31 > 37;
Console.WriteLine(value);
Here is the code that is required to build the same functionality using expression tree.
Expression expr = Expression.GreaterThan(
Expression.Constant(31),
Expression.Constant(37)
);
Console.WriteLine(Expression.Lambda<Func<bool>>(expr).Compile()());