In the first and third hour, 5 + 3 = <<5+3=8>>8 customers order the 3 egg omelettes.
In the second and last hour, 7 + 8 = <<7+8=15>>15 customers order the 4 egg omelettes.
To make the 3 egg omelettes, Theo needs 3 x 8 = <<3*8=24>>24 eggs.
To make the 4 egg omelettes, Theo needs 15 x 4 = <<15*4=60>>60 eggs.
To make all the omelettes, he needs 24 + 60 = <<24+60=84>>84 eggs.
#### 84