Question 170628
well if I am hearing the question correctly a full chapter was read by carly, Jo, and Sam.  If Carly read 1/3 and Jo read .25 or 1/4 . Let s be the portion of the chapter sam read.

(1/3)+(1/4)+s=1.....multiply by Least common multiple which is 12
:
4+3+12s=12........now subtract 4 and 3 from both sides
:
{{{highlight(s=5/12)}}} portion of chapter that Sam read