How to subtract one from the ninth question on page 35 of the second grade math book?

The ninth question on page 35 of the second volume of the second grade math book is "two numbers are added to get 12, and one of them is 7." What is the other number? " Ask for the subtraction of adjacent numbers, so that children can consolidate their basic mathematical operation ability. As a parent, you can help your child find another number according to the requirements of the topic. Idea: 12-7=5, so another number is 5 and the answer is 5. Children need to think carefully, understand the essence of subtraction, cooperate with textbook exercises, and gradually improve their ability to master mathematical knowledge. At the same time, parents can also help children deepen their understanding of mathematics knowledge from the aspects of addition remainder and inverse operation.