Answer: 49 cm^2
Explanation:
The length of the small pink square box will be:
L^2 = 9
L = sqrt( 9 )
L = 3
The length of the big pink square box will be:
L^2 = 16
L = sqrt( 16 )
L = 4
The length of the yellow square box will be:
4 + 3 = 7
The area of the third square box will be
A = 7^2
A = 49 cm^2