Answer:
t - s
------------
t + s
Explanation:
To solve a problem like this you need to flip the denominator and multiply
Step 1: Write the equation
s
1 - ------
t
--------------
s
1 + -------
t
Step 2: Flip it and multiply
s t
1 - ------ × 1 + -------
t s
Step 3: Multiply Across
s t -s + t t - s
1 - ------ × 1 + ------- = -------------- or ---------------
t s t + s t + s
I hope this helps!