Question

find the missing side length, in units, in the scaled copy.

original	scaled copy
10

Explanation:

Step1: Find the scale - factor

The scale - factor is found by dividing the corresponding side lengths of the scaled copy and the original. For the known sides, the original side is 5 and the scaled - copy side is 15. The scale - factor $k=\frac{15}{5}=3$.

Step2: Calculate the missing side length

Multiply the corresponding side length of the original rectangle by the scale - factor. The corresponding side in the original rectangle to the missing side is 10. So the missing side length $x = 10\times3=30$.

Answer:

30