For A, you have to do the parenthesis first. I did 2+(-3) which equals -5. Then, I added the 7 to the five and got 12. The reason that it is not 12 is because the +7 is greater than the -5.
For B, I got -3 because -4 - (-1) equals 3. The reason that it is three is because when you look at the positive negative chart, you can see that negative and negative equal positive. So, the answer would be 3.
For E, I got 4 NI because when I multiplied the 2*2 I got 4 then you add the numerals Ni. I am not 100% on this problem, that is kind of my guess.
Finally for F, I got 19. My equation above explains it. Once again, you have to add the parenthesis first, so, -7+(-12) equals 19. Like I said above. If you look at the negative positive chart, the number would be positive because both numbers are negative.
I forgot C above, so here it is. For C, I got the equation above by putting the numbers together. For instance, in the problem on the side, for C, it says -10=3+2. If you just add 3+2, you are going to get 5. I added negative five to it and there you go, you get negative ten.
The first and second problems are equal because 3 goes into 12 equally.
The decrease of the decimal rate -1.05 mm/year can be rounded to -1. You don’t need to round 2.48 because you’re multiplying by -1. Since -1.05 is negative and rounded to a greater value, the estimate could be adjusted to a slightly lesser value, maybe -2.5 or -2.6.