56cm²

2C +2L=30

C + L=15****** ( 1)

C = x

L= x + 1 *****

substituindo em ( 1 ) temos

x +x +1= 15

2x= 15- 1

2x=14

x=7***** ( C )

L= x+ 1 = 7 +1=8 *****

AREA = C* L

AREA=7 * 8 =56 cm² ******