Don't just focus on the algorithms of how to solve problems. If a child is struggling they very likely have a processing gap in the connection between one concept and the next. Teach them how to think about each step and understand WHY they are doing it. What does long division really mean and what other math concept is it related to? What do fractions represent from the whole? Why does adding or subtracting mean you have to change their denominator? How are decimals related to fractions, percents, ratios?

Have them start with pictures and sketches first and then move on to the more abstract elements of the process. Make factor trees and connect them to multiplication and division, but also addition and subtraction. Teach more than one way to find an answer, i.e. traditional multiplication, lattice multiplication, repeated addition multiplication, repeated subtraction for division. What is an integer? Under what real life conditions would they be used? Use measuring cups and spoons to teach the standard fractions. Make it more visual and auditory than abstract. I am sorry to go on for so long, but every year I have students who get tutored into memorizing steps rather than understanding why those steps work to arrive at the correct answer. Please, keep this in mind as you work with your student this summer. Good luck!