Hi, I can't seem to solve this problem. I can't find the last known variable (d). Here it is:

The interior angles of a quadrilateral are in an arithmetic squence. If the largest angile is 96 degrees, find the other angles.

So the formula is tn=a+d(n-1)

We know:

a=6

n=4? or 1?

d=?

tn=360

I don't know what d should be. Or am I suppose to solve for n? The answers at the back of the book are 84, 88, 92 meaning d is -4.

Please tell me how to approach this question. Thanks.