Answer:
15
Step-by-step explanation:
Simply subtract the smaller number from the bigger number, and divide by 2. Or add the two numbers together and divide by 2.
On the right side we have st which is the same as s*t or s times t
We want to undo the multiplication that is happening to s, so we have to divide both sides by t
d = s*t
d/t = s*t/t ..... divide both sides by t
d/t = s
s = d/t
Answer: Choice A)
Answer: 
Step-by-step explanation:
I looked it up on my calculator. I hope this helps!! :)