if ST = 6x, TU = 9, and SU = 9x, what is ST?

Question

If ST = 6x, TU = 9, and SU = 9x, what is ST?  I need help on this problem Because i have been stuck on this problem for at least three or four hours.

Answer 1

ST=6x

TU=9

SU=9x

ST=?

ST+TU=SU

6x+9=9x

9=9x-6x

9=3x

x=9/3

x=3

ST=6x=6*3=18

ST=18

ST+TU=SU

18+9=9x

27=9*3=27

Answer 2

ST = 6x <--- 1st equation

 

TU = 9  <---- 2nd equation

 

SU = 9x <-- Third equation

 

Dividing the third equation by the second equation:

S/T = SU/TU = 9x/9 = x

 

Plugging x = S/T into the first equation:

ST = 6(S/T)

 

ST^2 = 6S

 

ST^2 - 6S = 0

 

Factoring:

S(T^2 - 6) = 0

 

S = 0 or T^2- 6 = 0

 

S=0 or T^2 = 6

 

 S= 0  or    T = +or- sqrt(6)

 

Either way, ST = 0