400
Helen sat at her desk, whispering to herself as she worked out some numbers on the sheet of paper in front of her. "So nineteen and seven is twenty-six, and I write the two about the tens column," she murmured being careful not to be heard by anyone around her. She was certain she'd do well but didn't want to be accused of cheating.
What can we infer about what Helen is doing?
She is taking a math test.