Which correctly gives the expression using addition? - 17.9 - 4.2

a. - 17.9+4.2

b. 17.9+4.2

c. - 17.9 + (-4.2)

d. 17.9 + (-4.2)

c. - 17.9 + (-4.2)

The General rule for adding and subtracting numbers

1. Two integers with the same signs

Once 2 integers has the same sign, then just add the numbers.

For example

1. 1+1 = 2

2. 2 + 5 = 7

2. Two integers with different signs

When 2 integers has different sign, then find the difference

For example

1. 1-1 = 0

2. 2 - 5 = - 3

3. Two integers that vary in sign

When 2 integers vary in sign, then it will depend who which number carries the largest value

For example

1. - 3 + 2 = - 1

2. 2 - 1 = 1