In each group each of the letters A through H has one of the eight values listed. No two letters have the same value. The simple arithmetic problems are clues for determining the values of each letter. The three groups are independent.

Group 1
2,5,6,8,10,13,15,21
H+D=G
E-C=D
H+G=A
F+H=C
E-F=G
B+E=A

Group 2
3,4,5,9,12,13,17,22
C-A=B
H+D=A
D+F=G
F-A=E
C-D=G

Group 3
4,5,6,10,11,14,15,20
B-G=H
A+E=C
F-C=H
D-B=A
A+H=G
E+F=D