Calculate 18+6+20

When my son graduated from high school, he had to give a speech. He began by reading from his prepared text.
'I want to talk about my mother and the wonderful influence she has had on my life,' he told the audience. 'She is a shining example of parenthood, and I love her more than words could ever do justice.'
At this point he seemed to struggle for words. After a pause, he looked up with a sly grin and said, 'Sorry, but it's really hard to read my mother's handwriting.'