Question 161432
{{{(-7yt)/(3x)= Z /(18xt) }}}  

Treat this like solving a ratio

{{{(-7yt)/(3x)= Z/(18xt) }}} 
{{{(18xt)*(-7yt)/(3x) = Z }}}
{{{-126xyt^2/3x = Z }}}
{{{-42yt^2 = Z }}}

So the answer is
{{{(-7yt)/(3x)= (-42yt^2)/(18xt) }}}