Let's denote the price of an adult ticket as \( x \). According to the information provided, a child ticket for 12-and-under is $2 less than an adult ticket, so the price of a child ticket can be expressed as \( x - 2 \).
Maggie and her five friends make a total of 6 children going to the movies. The total cost for all the tickets can thus be expressed as:
\[ 6(x - 2) + x = 30 \]
Now, we can simplify this equation:
\[ 6(x - 2) + x = 30 \]
\[ 6x - 12 + x = 30 \]
\[ 7x - 12 = 30 \]
Next, we add 12 to both sides:
\[ 7x = 42 \]
Now, divide both sides by 7:
\[ x = 6 \]
Therefore, the price of an adult ticket is \( \boxed{6} \).