Final answer:
Sarah can correct the problem of the letters being too close together in the headers of her brochure by adjusting the letter spacing or kerning.
Step-by-step explanation:
To correct the issue of the letters being too close together in the headers of Sarah's brochure, she can adjust the spacing between the letters. This can be done by increasing the letter spacing or adjusting the kerning, which is the space between specific letter pairs. Sarah can do this manually by editing the headers in a design software or word processor, or she can apply a letter spacing option that is available in some software.