2–1/2+1/3–1/2+1/3—1/4=2-(1/2+1/2)+2/3-1/4=1+8/12-3/12=17/12
2–1/2+1/3–1/2+1/3-1/4=3/2+1/3–1/2+1/3-1/4=9/6+2/6–1/2+1/3-1/4=11/6–1/2+1/3-1/4=11/6-3/6+1/3-1/4=8/6+1/3-1/4=8/6+2/6-1/4=10/6-1/4=20/12-3/12=17/12