So, if you want to find the surface area of the cube, you have to find the areas of the sides.
First, you have to find the area of the front, back, right, left, bottom, and top of the cube
Then, you multiply
Front/Back = 5x3 = 15 x 2 = 30
Right/Left = 5x5 = 25 x 2 = 50
Top/Bottom = 3x5 = 15 x 2 = 30
Finally, you add it all up 30 + 50 = 80 + 30 = 110
Hope this helps! ;)