Eva is given the following steps:
1) Add two numbers.
2) Multiply the sum by 2.
3) The answer is 8.
She thinks the steps should be:
1) Add two numbers.
2) Multiply the sum by 4.
3) The answer is 8.
We add an extra step:
1) Add two numbers.
Extra step 1a) Adjust the sum to 2 by adding or subtracting.
2) Multiply the sum/difference by 4.
3) The answer is 8.
So the extra step is to work out the actual sum of the two numbers then reduce or increase it to get 2.
Let's suppose the two numbers are 6 and -2, so their sum is actually 4. The extra step would be to subtract 2:
1) Add 6 and -2.
1a) Subtract 2.
2) Multiply by 4.
3) The answer is 8.
The original question could have been:
1) Add 6 and -2.
2) Multiply by 2.
3) The answer is 8.