It doesn't make sense to talk about one "price" being twice as long as another! Is it possible that this should be "the piece of yellow yarn was twice as long as a piece of blue yarn?" If so, "after 90 inches has been cut" from a piece 230 inches long, it will be 230- 90= 140 inches long. Since that is "twice as long a piece of blue yarn", the blue yarn is 140/2= 70 inches long. So, initially, the piece of yellow yarn was 230- 70= 160 inches longer than the piece of blue yarn.
