gimana caranya menyelesaikannya ?

7.
a. keliling = 7+8+9 = 24
s = 24/2 = 12 cm
luas = √12x(12-9)x(12-8)x(12-7)
= √12x3x4x5
= √720
= 12√5 cm²

b. keliling = 3+5+8 = 16 cm
s = 16/2 = 8 cm
Luas = √8x(8-8)x(8-5)x(8-3)
= √8x0x3x5
= 0 cm²