Tolong d jwb yy kwan, pke caranya jga yy

keliling = tinggi+alas+sisimiring
30 = 3x+x+1+3x+1
30=7x+2
30-2=7x
28 : 7 = x
x=4

luas = (tinggixalas):2
        = ((3x)x(x+1) ):2
        = ((3x4)x(4+1)) :2
       = (12 x 5):2
       = 30 cm^2