Astudent thinks the sum of 4.3 and 8.4 is 12.7 because 4+8 is 12 and 3+4 is 7. the student then adds 3.7 and 2.6, then gets 5.13 because 3+2 is 5 and 6+7 is 13. identify the mistake in the student's procedure and explain why the procedure won't always work.