#### Answer

$x=-(t+r)$

#### Work Step by Step

We are trying to isolate $x$ in the equation $\frac{x+r}{t}+1=0$
First, we subtract $1$ on both sides of the equation: $\frac{x+r}{t}=-1$
Next, we multiply both sides of the equation by $t$: $x+r=-t$
Finally, we subtract $r$ from both sides of the equation: $x=-t-r=-(t+r)$