Question 900790
Let a to be the time taken for Company A to clear the land, while b to be the time taken for Company B to clear the land.


{{{a+b=9}}}
{{{a=b+4}}} ... Substitute into {{{a+b=9}}}
{{{(b+4)+b=9}}}
{{{b+4+b=9}}}
{{{b+b+4=9}}}
{{{2b+4=9}}}
{{{2b=9-4}}}
{{{2b=5}}}
{{{b=5/2}}}
{{{b=2.5}}} hours *It is already rounded off to the nearest tenth*


Therefore, Company B takes 2.5 hours to clear the parcel of land alone.