This answer is 290 because when you skip the math you would find the answer
Step 1. Divide both side by 16
100/16 = 6t - 13
Step 2. Dimplify 200/16 to 25/2
25/2 = 6t - 13
Step 3. Add 13 to both sides
25/2 + 13 = 6t
Step 4. Simplify 25/2 + 13 to 51/2
51/2 = 6t
Step 5. Divide both sides by 6
51/2/6 = t
Step 6. Simplify 51/2/6 to 51/2 * 6
51/2 * 6 = t
Step 7. Simplify 2 * 6 to 12
51/12 = t
Step 8. Simplify 51/12 to 17/4
17/4 = t
Step 9. Switch sides
t = 17/4
Completing the square follows the principle of taking

and converting it into

where d is the 'correctional number' as I like to call it - i.e. the number that converts the expanded bracket into the +c, since the expanded bracket will give us

.
In this case, 2/2=1 so we have the first part:

.
Expanding this gives us

. We need c to be 9, so we can just add 8.
Putting this together:

Now we can solve it more easily.
Rearranging:
B5 = -1 x (2 ^ 5 - 1)
B5 = -1 x (2 ^ 4)
B5 = -1 x 16
B5 = -16