Question 452181
"the output variable y is 38 less than the input variable x"
Therefore, y is 38 less than x. Since "is" is a signal word for "equals," and 38 less than x is the same thing as x minus 38, you can express this as y = x - 38
Next, since y is defined as the output, and the problem tells that the output value is 121, plug in 121 for y. 
121 = x - 38
Since the problem asks for the input, which it also states to be x ("the input variable x"), solve for x to find the input by adding 38 to both sides.
121 + 38 = x - 38 + 38
Simplify by adding 121 and 38. -38 and 38 cancel each other out.
159 = x
==> Therefore, the input value, x, is 159 when the output value, y, is 121.