Question 764681
Those are easier to deal with if rational statements like so:


{{{x/y=7/9}}}
.
{{{(x-12)/(y-12)=3/5}}}


Multiply each equation by its own lowest common denominator to simplify:
9x=7y and 5(x-12)=3(y-12)  giving   5x-60=3y-36 giving 5x-3y=-96


The system is then
{{{9x-7y=0}}} and {{{5x-3y=-96}}}
You could continue from here...