S1-S2=405

S1=405+S2

[tex]\frac{7}{2}=\frac{P1}{P2}[/tex]

[tex]\frac{S1}{S2}=(\frac{7}{2})^{2} =\frac{49}{4} =12,25------ > S1=12,25*S2\\[/tex]

405+S2=12,25*S2

405+S2-12,25*S2=0

405+S2(1-12,25)=0

405-11,25*S2=0

11,25*S2=405

S2=405/11,25=36 см²

S1=405+36=441 см²