There are several typing errors in your problem statement which makes understanding the problem parameters a bit confusing, but the following is what I will be using in my explanation. Let assign the following variables...
x=longest side
x-1=middle side, 1 foot shorter than
longest side, given
x/2=shortest side, given
P(Δ)=1919ft total perimeter, given
So....
P(Δ)=long+middle+short...definition of
perimeter
1919= x + (x-1) + 0.5x.....substitute side length
expressions
1919=2.5x-1.....combine like terms
1920=2.5x........add 1, both sides
2.5x=1920.......rewrite
∴ x=768.........divide both sides by 2.5
So...
longest side...................x=768 feet
middle side = x-1=768-1=767 feet
shortest side=.......768/2=384 feet
Let's check our solution....
P(Δ)=long+middle+short...total perimeter
1919=768+767+384...........substitute calc'd
side values
1919=1919..........................true, √check, our
solution is correct
for assumptions
made
Always check your solution and work!
Note:
Should the wording or values of your original problem be different, make the appropriate changes to the variable side length assignments. The calculation procedure remains the same.