This is an addition problem. We can list the formula, 1+6=7, and this number is 7.

Arithmetic is a branch of mathematics, or the primitive form of mathematics. It is a study of the basic properties of some digital operations. Commonly used operations are addition, subtraction, multiplication and division. Sometimes, more complex operations such as exponents and square roots are also included in the category of arithmetic operations. Arithmetic operations should be carried out according to specific rules.