Answer-
The value of x is 3 units.
Solution-
Here,
the volume of the prism with triangular base is 54 unit³
The base is a triangle with,
base = 4 units
height = x units
height of the prism = 3x
So, volume of the prism is,

And


Then,

As the volume is given as 54 unit³, hence



Ignoring -ve values, as length can not be -ve.
Therefore, the value of x is 3 units.