Answer: 26 units
Explanation:
Let's label the left side as side a, the bottom as side b, and the hypotenuse (the diagonal side) as side c.
As you can see, side a is 8 units, and side b is 7 units. To calculate side c, you need to plug both a and b in to the Pythagoras' theorem, which states that a² + b² = c².
> 8² + 7² = c²
> 64 + 49 = c²
> 113 = c²
> c = 10.63 which would round up to 11.
Now adding up all the sides together, a + b + c = 7 + 8 + 11 = 26 units