While you certainly can solve the problem by taking the square root of both sides, that will get ugly in a hurry. But there's a far simpler way of doing it. You know you can rewrite (t-4)2 as (t-4)(t-4). What do you get if you expand that out? And on the other side you have (t+4)2. What do you get if you expand that?. And then do you see an equation you can solve?