just had a quiz today and teacher threw on some questions that stumped me quite a bit and i'm trying to understand what i was supposed to do

1:

find the tangent line to the curve y = x-8/x+8 that is parallel to x-y = 8

so i differentiate the y='s equation to get (x+8) - (x-8) / (x+8)^2

that's where i'm stuck at and i don't get the parallel part

2: position of a particle is found by s = t^3 - 1.5t^2 - 2t. how long does it take to reach a velocity of 166 m/s

what i did was take the derivative of each individual term by the sum rule to get 3t^2 - 3t - 2

how do i find out when velocity reaches 166 with that equation?