How do you simplify #x/3 - x/7#? Prealgebra Fractions Fractions with Different Denominators 1 Answer Kushagra Oct 20, 2017 The LCM of 3 and 7 is 21 so #(x xx 7)/(3 xx 7) - (x xx 3)/(7 xx 3)# #(7x)/21-(3x)/21# #(7x-3x)/21# #(4x)/21# Answer link Related questions What is #3/8 -: 2/5#? What is #4##3/10##- ##3# #3/5#? What is #1/2 -: 3/4#? What is #1 1/4 xx 2 4/5#? What is the sum of #3 1/6 + (-5.5)#, expressed as a mixed number in simplest form? Josie had 1 gallon of ice cream. She used #3/10# gallon to make a chocolate milkshake and #3/10#... What is #4/5 -: 6 2/3#? How do you simplify #35/6 + 7/12 - 1 1/3#? How do you add #1/2 + 4/6#? How do you add #3 1/3 + 4 + 2/5#? See all questions in Fractions with Different Denominators Impact of this question 1720 views around the world You can reuse this answer Creative Commons License