Solve problems, including missing number problems, using number facts, place value, and more complex addition and subtraction

What this means, in plain words

Place value is the idea that a digit is worth a different amount depending on where it sits: the 4 in 40 is worth ten times the 4 in 4.

This is problem solving: the maths is met inside a situation, so the first job is working out which operation the question is asking for.

Addition puts amounts together to find a total. Subtraction takes one amount away, or finds the difference between two.