Why does (r-s) - (s-t) - (t-r) equal to 2r-2s? What are the steps?

(r - s) + (-s + t) + (t + r) The signs outside of the () indicate if the terms inside the () are positive or negative, you find this by multiplying the signs outside with the signs inside.

(r + r) (-s - s) (t - t) Add Like Terms together

r + r = 2r

-s - s = - 2s A negative minus a positive means you will add

t - t = 0

2r - 2r

Expand all the brackets out

When expanding a bracket with a negative in front, multiply all values in the bracket by negative one.

r - s - s + t - t + r

The t will cancel out

Combine like terms

r + r - s - s

2r - 2s