I found the missing diagram.
Given:
square ABCD = area of 144 cm²
MA = 6
Side length of ABCD = √144 cm² = 12 cm
Based on the diagram I found, right triangles are formed between the two squares. We need to use the Pythagorean theorem to solve for the hypotenuse which is the side length of square MWTH.
Long leg = 12 cm + 6 = 18 cm
short leg = 6 cm
18² + 6² = c²
324 + 36 = c²
360 = c²
√360 = √c²
18.97 = c
The side length of MWTH is 18.97 cm. It area will be 360 cm²