We can express this as:
x + 2x = £3.45
We can solve for x with no additional work.
x + 2x = £3.45
3x = £3.45
3x/3 = £3.45/3
x = £1.15
Im guessing you're British by the use of the £ symbol, and I don't understand what "dearer" means as in America we don't use that term. I'll just give you both values.
x = £1.15 (this is the first book)
2x = £2.30 (this is the second book, which costs twice as much as the first.)
