The guests ate 28 / 4 = <<28/4=7>>7 cucumber sandwiches.
The guests ate 12 / 2 = <<12/2=6>>6 egg sandwiches.
They ate a total of 7 + 6 = <<7+6=13>>13 sandwiches.
They ate a total of 13 x 2 = <<13*2=26>>26 slices of bread.
#### 26