11 1/2+6 4/5 equals? So, you have to make each fraction have the same denominator. So, you would notice that they have in LCD (least common denominator )which is 10. So you're new fractions are 11 5/10+ 6 8/10. 11+6=17. 5/10+8/20=13/10. Which simplified it would be 1 3/10. 17+1 3/10 equals 18 3/10. 18 3/10 -3 3/10 equals 15. 15 is the answer.