To simplify the given expression completely, we can try to factor the numerator and the denominator individually and then cancel out any common factors.
Let's start with factoring the numerator: x^2 - 17x + 70.
To factor this quadratic expression, we need to find two numbers whose product is 70 and whose sum is -17 (since the coefficient of x^2 is 1). These numbers are -10 and -7.
So, we can rewrite the numerator as (x - 10)(x - 7).
Now let's factor the denominator: x^2 - 18x + 80.
Similarly, we need to find two numbers whose product is 80 and whose sum is -18. These numbers are -10 and -8.
So, we can rewrite the denominator as (x - 10)(x - 8).
Now, we can simplify the whole expression by canceling out the common factor of (x - 10) in the numerator and denominator:
start fraction, (x - 7), divided by, (x - 8), end fraction.
So, the simplified expression is (x - 7)/(x - 8).