1/2 + 1/3= 1/2+1/5= 1/3+1/4 = 1/4+1/5= 1/2 +1/4= 1/3+1/6= 1/2+1/6= 1/4+1/8=
1/2+1/3=1/5=5 1/2+1/5=1/7=7 1/3+1/4=1/7=7 1/4+1/5=1/9=9 1/2+1/4=1/6=6 1/3+1/6=1/9=9 1/2+1/6=1/8=8 1/4+1/8=1/12=12