@Ummi_eee Assume that two pieces of pie shape is A and B, then top rectangle is C and D for the bottom one.
So, the basic math equation in this type of question is: A + B = C x D
To find:
A = (C x D) - B
B = (C x D) - A
C = (A + B) : D
D = (A + B) : C
Hopes that helps. Keep practicing