Each operation in an algorithm must be sufficiently clear so that it does not need to be simplified. The meaning of “sufficiently clear” depends on who or what the algorithm is written for. The instruction
average the two numbers
would be clear to most humans. However, the same instruction is ambiguous to a computer because the computer has no basic operations for averaging. For a computer, the algorithm would have to be expressed in terms of operations that can be carried out by programming language statements - adding the two numbers and dividing the sum by two.