Answer: Choice C
The student solved the problem incorrectly. The student should add 12.7 to both sides of the equation to isolate the variable, y.
================================================
Explanation:
We add 12.7 to both sides to undo the "minus 12.7"
We apply the inverse operation to whatever is happening to x.
As another example, solving x-2 = 10 leads to x = 12 after adding 2 to both sides to undo the "minus 2".
------------
The student's steps should look like this
y - 12.7 = 32.75
y-12.7+12.7 = 32.75+12.7
y = 45.45
Notice on the left side of the second step, we have the -12.7+12.7 become 0 and go away.
