First step, divide 6 from both sides.
t/6=r^2+1
second step, subtract 1 from both sides
t/6 -1=r^2
Now take the square root of each side.

Done!
-16/-2
Divide numerator & denominator by 2
-8/-1 = 8
Answer:
Hi. I am a math teacher. Your correct answer is 210. You're welcome!
Let's plug the values and see which couple satisfy the equation: since
, if we plug the values from the first option
we have

which is correct.
If we plug the values from the second option
we have

which is not correct
If we plug the values from the third option
we have

which is not correct
If we plug the values from the fourth option
we have

which is not correct
So, the answer is the first one.