A - B = C
*
D : E = F
=
G + H = I
Solution:
First of all no variable can be zero.
Therewise two variables would be equal.
The key are the two multiplications.
C * F = I
E * F = D
As only two products 2*3 and 2*4 are smaller than 10
we get the two cases:
F = 2, C = 3, E = 4 and
F = 2, C = 4, E = 3.
The rest is easily filled in.
The second case gives the unique solution
9 - 5 = 4
*
6 : 3 = 2
=
1 + 7 = 8