The phrase "not difficult to guess" is correct and usable in written English.
You can use this phrase to refer to something that is obvious or easily guessed, for example: "The answer to the test question is not difficult to guess."
It was not difficult to guess why Moscow might want to hack OPCW communications.
And it is not difficult to guess where he is headed.
It is not difficult to guess which animal the town of Sawai Madhopur has tethered its fortunes to.
And if our largest-selling newspaper supports your political party … well, it's not difficult to guess the rest.
But it is not difficult to guess what is propelling this 75-year-old Swiss who presides over the evolution of soccer.
After 10 Nbd2, it is not difficult to guess that Cicak's timid Queen's Pawn Opening was chosen with a heavy heaping of Timman terror in mind.
It isn't difficult to guess which of the world's vineyards might command dizzying prices.
But it isn't difficult to guess why the President chose instead to endorse the new phase of the financial rescue plan that Treasury Secretary Timothy Geithner unveiled last week.
Even for readers who have not witnessed William Thornhill's past deeds, the nature of this buried truth will not be difficult to guess – this is Australia in the early 19th century, after all, and even as a child Sarah is conscious of her father's deep unease about the Aborigines living lives of poverty in the bush nearby.
Actually it is not so difficult to guess what Washbrook would have thought of this night-time spectacular played out on a building site.
Hell, maybe I could even give her some of the money!" It is not too difficult to guess, knowing what we already know of the glimmer of goodness that lies inside Junior's heart, whether he turns in Mary Iris, but what flows from that decision is a good deal less predictable.
