Rachel Riley is Countdown's queen of maths, and the star has announced that she will be releasing a new book to help adults with the subject.MORE: Rachel Riley's favourite makeup products revealed - and we want the lotAt Sixes and Sevens is due to be released in October and will see the 35-year-old tackling some of the harder parts of maths to make them more accessible.WATCH: Rachel Riley thrills fans with surprise announcementPart of the synopsis reads: "Discover how to divide and conquer, make