Recall that with base- ten blocks, 1 long = 10 units, 1flat = 10 long, and a block = 1 unit. Then what number does 5 flat, 17long and 5 units represent represent ?

To find the number that is represented by 5 flat, 17 long, and 5 units, we need to convert each type of base-ten block to its corresponding value and then add them together.

We know that:
1 flat = 10 long
1 long = 10 units

We can start by converting the 5 flats to longs:
5 flat = 5 * 10 long = 50 long

Now, we add the converted flats to the given 17 longs:
50 long + 17 long = 67 long

Finally, we add the 5 units to the total:
67 long + 5 units = 67 long and 5 units

Therefore, the number represented by 5 flat, 17 long, and 5 units is 67.5.

$\textbf{Answer: 67.5}$