Question 770255
Let the weight of box A to be a, of box B to be b and of box C to be c.
Box B is {{{3&1/2}}} kg more than box A means {{{b=a+3&1/2}}}.
Box C weighs {{{5&1/3}}} kg more than Box B means {{{c=b+5&1/3}}}.
The total weight of three boxes is {{{60&1/2}}} kg means {{{a+b+c=60&1/2}}}.
{{{a+b+c=60&1/2}}} --> Equation 1
{{{b=a+3&1/2}}}
{{{a=b-3&1/2}}} --> Equation 2 ... Substitute {{{a=b-3&1/2}}} into Equation 1
{{{c=b+5&1/3}}} --> Equation 3 ... Substitute {{{c=b+5&1/3}}} into Equation 1
{{{a+b+c=60&1/2}}}
{{{(b-3&1/2)+b+(b+5&1/3)=60&1/2}}}
{{{b-3&1/2+b+b+5&1/3=60&1/2}}}
{{{b+b+b-3&1/2+5&1/3=60&1/2}}}
{{{3b-3&1/2+5&1/3=60&1/2}}}
{{{3b+1&5/6=60&1/2}}}
{{{3b=60&1/2-1&5/6}}}
{{{3b=58&2/3}}}
{{{3b=176/3}}}
{{{cross(3)b/cross(3)=(176/3)/3}}}
{{{b=(176/3)*(1/3)}}}
{{{b=176/9}}}
{{{b=19&5/9}}} ... Substitute {{{b=19&5/9}}} into Equation 2
{{{a=b-3&1/2}}}
{{{a=19&5/9-3&1/2}}}
{{{a=16&1/18}}}
Therefore, the weight of box A is {{{16&1/18}}} kg.