http://www-k6.thinkcentral.com/content/hsp/math/hspmath/na/common/itools_int_9780547584997_/main.html?module=fractions&activity=6 (iTools: Add:  Fraction Bars)

 

http://www-k6.thinkcentral.com/content/hsp/math/hspmath/na/common/itools_int_9780547584997_/main.html?module=fractions&activity=8 (iTools:  Subtract:  Fraction Bars)

 

http://www-k6.thinkcentral.com/content/hsp/math/hspmath/na/common/mega_math_9780547585062_/megamathcd6/cm/launch.html?strActivityName=g36_3_1_D&strAssignID=1 (Fraction Flare Up Level D)