Question 609370
This is a work problem. I think of it as a 
rate problem.
Peter's rate is {{{ 25/4 }}} sq yds / hr
John's rate is {{{ 25/5 }}} sq yds / hr
Add their rates to get their rate together
{{{ 25/4 + 25/5  = x / 8 }}}
Multiply both sides by {{{ 4*5*8 }}}
{{{ 25*5*8 + 25*4*8 = 4*5*x }}}
{{{ 25*( 40 + 32 ) = 20x }}}
{{{ 4x = 5*72 }}}
{{{ 4x = 360 }}}
{{{ x = 90 }}}
Together they can make 90 sq yds in 8 hrs