Since there is no value for either X or Y given, you can only change the formula around to equal X.
y=45x+38
First move the 38 to the left side by canceling it out (subtract 38 from both sides).
y-38=45x+38-38
So now we have:
y-38=45x
Now isolate the x on the right side by dividing both sides by 45.
(y-38) / 45 = x
So,
x = (y-38) / 45
(If the answer you’re looking for is a specific number, then the value for X or Y needs to be given!)