(3 1/2 + 16 1/2)/(1/3-2 1/3)312+161213−213
color(white)("XXX")=(7/2+33/2)/(1/3-7/3)XXX=72+33213−73
color(white)("XXX") = {(7+33)/2}/{(1-7)/3}XXX=7+3321−73
color(white)("XXX")= (40/2)/(-6/3)XXX=402−63
color(white)("XXX") = 20/(-2)XXX=20−2
color(white)("XXX") = -10XXX=−10