y and a are different names for the variable x. There is only one variable; y and a are other names you can use to mean the exact same variable.
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x++; // adjust the value of x
y++; // adjust the value of y, which is just another name for x, so adjust the value of x
a++; // adjust the value of a, which is just another name for x, so adjust the value of x
No, it isn't different. What I said is exactly what happened.
y++ //adjust the value of y, which is just another name for x so adjust the value of y by 2
What are you talking about? That's nonsense. y++ means increase the value of y by one. Not by two. The value of y was ALREADY increased when we did x++, because y is just another name for x. y and x mean the exact same object in the exact same piece of memory.