Find the Requested Partial Derivative $( \partial z / \partial x ) _ { y }$

Multiple Choice

Find the requested partial derivative.
- $( \partial z / \partial x ) _ { y }$ at $( x , y , z ) = ( 1,1,1 )$ if $z ^ { 3 } + 6 x y z = 7$

A) $- \frac { 1 } { 2 }$
B) $- \frac { 4 } { 3 }$
C) $- \frac { 2 } { 5 }$
D) $- \frac { 2 } { 3 }$