Awire, 224 cm long, is cut into three pieces. the first is twice as long as the second. the third is 1/2 as long as the second. how long is the second piece?

If I did this correctly then the answer should be: 

Lengths of first, second, and third pieces are f, s, and t

f+s+t=224
f=2s
t=0.5s

2s + s + 0.5s = 224
3.5s = 224
s = 224/3.5 = 64.

The second piece is 64 cm long.

X,y,z
x+y+z=224

x is 2 times as long as y
x=2y

z is 1/2 times 2nd
z=y/2

sub 2y for x and y/2 for z

2y+y+y/2=224
3y+y/2=224
times 2 both sides
6y+y=448
7y=448
divide both sides by 7
y=64

the 2nd piece is 64 cm