If we know that 6 things cost 2.99 and we want to know unit price we just have to divide 2.99 by 6.
So 2.99:6=0.49$ - its the result.
Now we can say that his sister is not correct, because price is different that 2$/unit.
Well consecutive means in a row, or one number after the other (for ex. 1,2,3,4). And for this equation it's asking for 4 consecutive numbers of which the sum is -26. To get this you just need to go on a calculator and just try some consecutive numbers, you'll get it pretty quickly. The answer is -5,-6,-7,-8. The sum of those numbers is -26.
Hope this helps!
B. I guessing let me kno if it’s wrong