Let the price of one movie ticket without the coupon be \( p \). Since each friend uses a $2-off coupon, the price each friend pays for a ticket is \( p - 2 \).
Since there are six friends, the total amount they spend is:
\[ 6 \times (p - 2) = 42 \]
We can simplify this equation:
\[ 6p - 12 = 42 \]
Next, we'll add 12 to both sides of the equation:
\[ 6p = 42 + 12 \]
\[ 6p = 54 \]
Now, divide both sides by 6 to solve for \( p \):
\[ p = \frac{54}{6} = 9 \]
Thus, the price of one movie ticket without the coupon is \( \boxed{9} \).