1/(x+10)(x+11)+1/(x+11)(x+12)+1/(x+12)(x+13)+1/(x+13)=1/14
∴1/(x+10)-1/(x+11)+1/(x+11)-1/(x+12)+1/(x+12)-1/(x+13)+1/(x+13)=1/14
∴1/(x+10)=1/14
∴x=4