Let's simplify the expression using the properties of logarithms:

log7 x = log7 (14) - log7 (98)

We can rewrite the right side of the equation using the properties of logarithms:

log7 x = log7 (14/98)

Now, simplify the expression inside the logarithm:

log7 x = log7 (1/7)

Since 1/7 is equivalent to 7^-1, we can rewrite the expression as:

log7 x = log7 (7^-1)

Using the property of logarithms where log_a a^b = b, we get:

log7 x = -1

Therefore, the simplified expression is log7 x = -1.