Question 994292
b kgs bananas
m kgs mangos

{{{(75*b+120*m)/(b+m)=100}}}
Let b=5.
{{{(75*5+120m)/(5+m)=100}}}


{{{120m+5*75=100(m+5)}}}

{{{120m+5*75=100m+500}}}

{{{20m=500-5*75}}}

{{{4m=100-75}}}

{{{4m=25}}}

{{{m=25/4}}}
{{{highlight(m=6&1/4)}}}