Question 290780
  
  The total No. of mowers = 30
  
  Let the No. of small mowers be = x;   So,
  the No. of large mowers  = (30-x)

  Sale of small mowers = ($249.99)(x) and the
  Sale of large mowers = $329.99(30-x)
                       = $9899.70 - 329.99x

  Total sale = $249.99x + $9899.70 - 329.99x =  $8379.70
             =  -80x + $9899.70 = $8379.70.   (By transposing,
             $9899.70 - $8379.70 = 80x
             =  $1520.00  =  80x.  Therefore,
             =   x = $1520/80 = 19 small mowers.
  So the large mowers (30 - x) = 30 -19 =11 large mowers.  

  Small mowers = 19;  Large mowers = 11.  Answer.  

I think you have understood this.  If not, feel free to contact me anytime for any doubts in maths online.

God Bless you.  

gsm