If two numbers have a difference of 142, and one of them is x + 142, then the other is

We are given information:
y - x = 142
y = x + 142

Now we can insert second equation into first to solve it for x:
x + 142 - x = 142
142 = 142

We can clearly see that this is true. Both sides are same. Also, neither right side or left side contains x or y. x can be any real number.
x∈R
This means that y is also real number that satisfies the given equation.