What is bk + m = j correctly solved for b?

[10 points, algebra 2-simplifying complex fractions]according to my answer key the restrictions are -1 and 4. but why not positive 1?

If you have the following equation, 2/3x+5/6-x=2-3/4x what would you multiply each term by to get rid of all the fractions

Which answer goes into the box? (90° clockwise rotation, 90° counter clockwise rotation, translation, or glide reflection)