Ask your child to explain the strategy (or strategies) that he or she is trying to use. It can be helpful to the student to express their thoughts in words, which may help lead to discovering what he or she is try to figure out without you having to do anything.
If you don't understand the strategy, that's okay! Remember, teachers are often presenting students with problems that can be solved using different paths to arrive at a right answer, but there are also problems presented with more than one right answer, too. The goal of a homework assignment is for students to practice applying the strategies from class to reinforce understanding. The ultimate goal then is for students to later transition by building on those skills when they learn new concepts later.
If your child continues to struggle with their math assignments, please contact their teacher. Most likely, your child's teacher may have a plan in place already for children who are having trouble with a concept. By letting the teacher know there was a problem with the homework, rather than trying to fix it yourself, together as a team you can both decide upon the best next steps for your child.
Encourage your child to visit the “Math Resources” areas in the student portal. Here you'll find information about extra help opportunities at the middle school and high school, DreamBox Learning for K-3, as well as math games that can help strengthen your child's understanding of math concepts from kindergarten to the high school level.