Question 82318
x=y+3
10x+y=10y+x+54 now substitute (y+3) for x  & solve for y.
10(y+3)+y=10y+(y+3)+54
10y+30+y=10y+y+3+54
11y-11y=57-30
0=27 this would indicate that every set of numbers results in a difference of not 54 but 27. Thus:
96
-69
---
27 

85
-58
----
27

74
-47
---------
27
&

30
-03
---------
27