The problem asks us to identify which of the given equations are equivalent to the equation $tu = 5$. We need to use properties of equality to determine the equivalent equations.

1. Problem Description

The problem asks us to identify which of the given equations are equivalent to the equation $tu = 5$. We need to use properties of equality to determine the equivalent equations.

2. Solution Steps

We are given the equation $tu = 5$. We need to check each of the other equations to see if they are equivalent to this one.

* $tu + 3 = 9$

Subtract 3 from both sides:

$tu + 3 - 3 = 9 - 3$

$tu = 6$

Since $tu=6$ and not $tu=5$, this equation is not equivalent.

* $tu + 13 = 18$

Subtract 13 from both sides:

$tu + 13 - 13 = 18 - 13$

$tu = 5$

Since $tu=5$, this equation is equivalent.

* $8 + tu = 12$

Subtract 8 from both sides:

$8 + tu - 8 = 12 - 8$

$tu = 4$

Since $tu=4$ and not $tu=5$, this equation is not equivalent.

* $tu + 5 = 9$

Subtract 5 from both sides:

$tu + 5 - 5 = 9 - 5$

$tu = 4$

Since $tu=4$ and not $tu=5$, this equation is not equivalent.

3. Final Answer

The only equation equivalent to $tu=5$ is $tu+13=18$.