Answer:
RECT is similar to SQUA since their corresponding angles are the same size, and the side lengths of RECT are three times the corresponding side lengths of SQUA (their corresponding sides are in the same ratio).
Explanation:
In similar shapes:
- Corresponding angles are the same size.
- Corresponding sides are always in the same ratio.
Since RECT and SQUA are both rectangular, their corresponding angles are the same size.
If RECT is similar to SQUA then their corresponding sides will be in the same ratio:

From inspection of the given diagram:
- RE = 18
- EC = 10.5
- SQ = 6
- QU = 3.5
Substitute these values into the ratio:

Therefore:

Cross multiply:


As the equation is true, this proves that RECT ~ SQUA.
Note: The side lengths of RECT are three times the corresponding side lengths of SQUA.