Let the number of points for each multiple choice question be \( x \).
Gretchen's total score can be calculated as follows: \[ \text{Gretchen's Score} = 18x + 19 \]
Ezia's total score can be calculated as: \[ \text{Ezia's Score} = 15x + 31 \]
Since both received equal scores, we can set the two expressions equal to each other: \[ 18x + 19 = 15x + 31 \]
To solve for \( x \), first, we will get all terms involving \( x \) on one side and constant terms on the other side: \[ 18x - 15x = 31 - 19 \] \[ 3x = 12 \]
Now, divide by 3: \[ x = 4 \]
Thus, the points for each multiple choice question is \( \boxed{4} \).
To verify, we can calculate both Gretchen's and Ezia's scores using \( x = 4 \):
Gretchen's score: \[ 18 \times 4 + 19 = 72 + 19 = 91 \]
Ezia's score: \[ 15 \times 4 + 31 = 60 + 31 = 91 \]
Both scores are equal, confirming that our solution is correct. Each multiple choice question is worth \( \boxed{4} \) points.