Your child at this stage is all set to understand the number line and mental math strategies and he possesses the skills needed to develop strategies and solve more complex math equations.
What you need to know
As a parent, you need to identify the ways in which you can teach your child the concepts of solving different problems in math. Introduce him to the first concept- number line, wherein he can interpret how the numbers are arranged and what comes after what. Begin to make mathematical discussions as a part of your everyday routine. You will then notice your child developing his own math strategies and when you have provided him with a solid foundation, he will naturally use what he knows to invent other strategies that work well for him and others.
What you can do
Counting on, is probably the first mental math strategy that is to be taught. If you have the equation 5+3, encourage them to start with 5 in their head and further count 6, 7 and 8 and so on. Counting doubles is the next concept to be taught. Encourage them to build a strong foundation by adding 2+2; 5+5 and so on. This will give a strong basics to mental counting and counting doubled plus one. The doubles plus one strategy is a natural progression from the former. It includes using a known fact and building on it. In an equation, 5+6 your child will be able to understand that 5+5 gives 10 and adding one more will give the correct answer 11.
This strategy will need a little bit of extra teaching efforts, but will surely be worth it! Making ten strategy involves memorizing the number combinations that add to 10 like 7+3, 5+5 or 6+4 and so on.