help me with a simple math formula I can't figure out

Question

I have 6 pictures all 13" wide that I would like to space evenly across a 136" wide wall and its driving me crazy because I'm sure its a simple formula to figure out but could someone please tell what the distance is

Answer 1

The 6 pictures together are 6*13 = 78 inches wide.  The wall is 136 inches wide, so you have 136 - 78 = 58 inches of blank wall.  You have seven gaps, five between the 6 pictures and two on either end.

 

(58 inches)/(7 gaps) ≅ 8.3 inches per gap

 

The first picture is places 8.3 inches from the wall on the left; there is a gap of 8.3 inches between each picture, and the last picture is 8.3 inches from the wall on the right.