heidi subtract 9 from 17. first she adds to get 10.then she added again to find her answer is heidi correct Heidi is not correct to add blank then you add blank more to get 10 to 17 the answer is

Heidi wants to compute:

17 - 9.

First, she adds to get 10, (we want to subtract 10, this is easier than subtracting 9) then she can do:

17 - 9 + 0

adding zero does not change the sum

1 - 1 = 0

then:

17 - 9 + 0 = 17 - 9 + 1 - 1

Now we can do:

17 - 9 - 1 + 1

17 - (9 + 1) + 1

17 - 10 + 1

(17 - 10) + 1

7 + 1 = 8

Then, first she needs to add -1, in order to subtract 10, and then she must add 1. As we added a number and its inverse, in total we added zero, so the sum did not change, but was easier to compute.

Then, you need

it is a. 4.2 because 7.6-3.4 gets the remaining length of 4.2. i might be wrong but i am pretty sure this is the answer.