ГДЗ по математике за 4 класс Моро, Бантова, Бельтюкова - uPortfolio
For particularly tough sections, such as "Pages for the Curious" ( Странички для любознательных ), video walkthroughs on YouTube can provide a much clearer explanation than a static text solution.
Fourth grade is often the "transition year" where math moves from concrete to abstract. Staying patient and using these digital resources as a rather than a shortcut will help build the foundational skills needed for middle school.