3x23+a=92 => 69 + a = 92 => a = 92 - 69 => a=23
bx7+3=80 => 7b + 3 = 80 => 7b = 80-3 => b = 77 : 7 => b=11
6xc+8=80 => 6c + 8 = 80 => 6c = 80-8 => c = 72 : 6 => c=12
dx7+1=82 => 7d + 1 = 82 => 7d = 82-1 => d = 81 : 7 => d=11,57
9-e+1=100 => 10 - e = 100 => -e = 100-10 => e = -90
fx7+2=100 => 7f + 2 = 100 => 7f = 100-2 => f = 98 :7 => f=14