Question 1120748
{{{a+b+c+d=280}}}

{{{a=b+40}}}

{{{a-40=b}}}

{{{c=2b+20}}}

{{{d=c/6}}} Substitute b+40 for a,

{{{b+40+b+c+d=280}}}

{{{2b+40+c+d=280}}} Substitute 2b+20 for c,

{{{2b+40+2b+20+d=280}}}

{{{4b+60+d=280}}} Substitute (2b+20)/6 for d,

{{{4b+60+(1/3)b+(10/3)=280}}}

{{{(13/3)b+(190/3)=280}}}

{{{(13/3)b+(190/3)=840/3}}}

{{{(13/3)b=650/3}}}

{{{highlight(b=50)}}} 

{{{a-40=50}}}

{{{highlight(a=90)}}}

{{{c=2(50)+20}}}

{{{highlight(c=120)}}}

{{{d=120/6}}}

{{{highlight(d=20)}}} So the masses are a=90,b=50,c=120,and d=20. Check:90+50=140+120=260+20=280.90-30=60. 50+10=60. 120/2=60. 20*3=60. Correct.