First i found A, by dividing 8 by 4, then A=2
Then i found d, by solving the equation 2D+2A=16 and since we know A=2 then 2D+4=16 -> 2D=12 -> D=6
Next i found B, by solving the equation 2A+D+B=11 replacing the values for A and D that we already found: 4+6+B=11 ->B=11-6-4 ->B=1
After that, i found C by solving the equation A+2C+D=18 replacing the values for A and D that we already found: 2+2C+6=18 -> 2C=10 -> C=5
Next i found E by solving the equation 2A+B+E=9 replacing the values for A and B that we already found: 4+1+E=9 then E=9-4-1 then E=4
Then i found F, by solving the equation E+B+F+C=17 replacing the values for E, B and C that we already found: 4+1+F+5=17 then F=7
To finish i found G by solving the equation B+A+G+C=11 replacing the values that we already found in the previous steps: 1+2+G+5=11 then G=3