Ok, so first work backwards. How do you work out the area? Height x Base/ 2 = area. The area is 28. So 28 x 2 = 56. Now what x what = 56. The first thing that comes to my mind is 4. So what x 4 = 56. 56/4 = 14. 14 is also 10 greater than 4. So the height of the triangle is 4cm, the base of the triangle is 14cm and the area is 28.
Height = 4cm
Base = 14cm
I hope this helped :)