Cari owns a horse farm and a horse trailer that can transport up to 8,000 pounds of

Given:
5 horses with a combined weight of 6,240 pounds
horse trailer has a limit of 8,000 pounds of horse and tacks.

Find the weight of tack, t, for each horse that Cari can allow.

5t + 6,240 <  8,000

5t + 6,240 < 8,000
    - 6,240    -6,240
5t              < 1,760
÷5                 ÷5    
 t               <  352

Each horse can carry a tack that weighs no more than 352 pounds. 

Any tack that weighs beyond 352 pounds is will exceed the maximum carrying capacity of the horse trailer.