Question 1092734
 Use {{{xyz}}} as a common denominator,
{{{(x-y)/xy + (x-z)/xz - (z-y)/yz=(z(x-y))/xyz + (y(x-z))/xyz - (x(z-y))/xyz}}}
{{{(x-y)/xy + (x-z)/xz - (z-y)/yz=((xz-yz) +(xy-yz)-(xz-xy))/xyz}}}
{{{(x-y)/xy + (x-z)/xz - (z-y)/yz=(2xy-2yz)/xyz}}}
{{{(x-y)/xy + (x-z)/xz - (z-y)/yz=2(x-z)/xz}}}
{{{(x-y)/xy + (x-z)/xz - (z-y)/yz=2(1/z-1/x)}}}