tolong memakai caraaaa

kll = a+b+c
30 =3x + 3x+1+x+1
30=7x+2
30-2=7x
28/7=x
x=4

sisi a=3x =3(4)=12
sisi b=x+1=4+1=5
sisi c=3x+1=3(4)+1=13

l=a×t/2
l=5×12/2
l=30 cm²