Related Post: 5 7 X 3 1 2 7 5 X 1 3 2 8 5 X 1 )- 7 3 X 1 )+ 2x 5 2x 4 )= 7 X 1 )- 3 3 4 5 X 7 1 2 1 − 7 5 X 3 20 X 7 3 1 3x 2 5 5 X 3 )- 7 3 1 X )+ 21 7 X 5 )+ 1 2 3 2x 1 5 1 2 X 7 3 4 Envelopes