Keep the first denominator to make the animation look smoother.
Keep the first denominator to make the animation look smoother.

Test Plan:
http://localhost:3000/?start=(x+2)/5
Select everything, choose split fractions.

See that the first 5 is kept during the animation.

kevinbarabash/mobile-mathipulator,kevinbarabash/mobile-mathipulator,Khan/algebra-tool,Khan/algebra-tool