If $a\times b\times c=t$ and I change $a$, $b$, and $c$, how do I calculate the effect of each change.

I believe the equation is: $(a+\Delta a)(b+\Delta b)(c+\Delta c)=(t+\Delta t)$, and then I solve for $\Delta a$, $\Delta b$, and $\Delta c$.

Is this correct? And how do I describe what I'm solving for?