Dyslexia is best known as a condition where people have difficulties recognising and spelling words, but it can also affect ability in maths. It is unlikely a dyslexic child will find word problems easy due to the way their brain processes language and information.
Dyslexic pupils often have short and/or long-term memory issues, which means that retaining maths concepts and the rote learning of multiplication tables becomes problematic. Repeated practice and reinforcement of different concepts is vital.
There has been more educational research in recent years which show links between dyslexia and difficulties with maths. The general term used for this is dyscalculia. This may well apply to your son. These links are sometimes not picked up in schools and dyslexic children are often just considered low-ability mathematicians.
Remembering multi-step written procedures for methods such as multiplication and long division can be difficult for dyslexic children and inconsistencies of rules are confusing - for example, division sums start from the left but addition and subtraction sums start with the units column at the right-hand side.
There are many positive things that teachers and parents can do to help children with dyscalculia. One is to give your son a list of strategies he can use when attempting a maths problem. Also, training him to read a word problem aloud to himself and underlining key words will help his brain to make sense of the information.