Using the arithmetic formula a1 + (n-1) d, a1 being the first term, n being the number you’re looking for and d being the common difference, you will get the answer of -57.
Here’s the work:
27 + (29 - 1) -3
27 + (28) -3
-57
She underestimated by 60 cents. To get this answer all you need to do is multiply 1 dollar times 12 which is $12 and then multiply $.30 by 12 and that gives you $3.60. Then you add the $12 to the $3.60 and that gives you $15.60 which is 60 cents over the estimation.
The rules are


Let me show you why with a couple of examples: suppose we want to multiply

Since powers are just repeated multiplications, we have

Similarly, we have

the greatest common factor (GCF) of 12, 24, and 48 is 12.