The area of a rhombus can be found by using the formula:
A = (1/2)(d1)(d2)
Area = (1/2)(8)(6)
Area = 24 cm^2
Your other option is to remember that in a rhombus the diagonals bisect each other, and form right triangles. So you have 4 right triangles each with sides of 4 cm (1/2 of 8 cm) and 3 cm (1/2 of 6 cm). 4 x [(1/2) x (4)(3)] = 4 x 6 = 24 cm^2.