Not all individuals with dyslexia have problems with mathematics. I have, however, seen a few dyslexic students who don’t seem to understand mathematics.
Individuals with dyslexia who have difficulty with mathematics are quite often misdiagnosed as having dyscalculia. Some children with dyslexia have problems with mathematics because what they have been taught makes no sense to them. Most teachers hardly take the time and trouble to make sure that these children do understand the basic principles. This seems to be the same problem with them learning how to read in English. Their basic problem is that they do not understand and their minds shut down.