Label the vertices of the quadrilateral A, B, C, D. Angle C is supplementary to the angle of measure 60 degrees, so its own measure is 120 degrees.
AD and BC are parallel, as are AB and CD, so ABCD is a parallelogram. This means angle A also has measure 120 degrees. The angle adjacent to the one with measure
, part of angle A, then has measure
.
The three angles above the line through vertex A are supplementary, so we have



Answer:
yes
Step-by-step explanation:
because we are simply "adding" 2 negative numbers.
-8n + -7 = -7 + -8n
as long as we flip the terms around with their signs, the commutative principle of addition applies.
what we CANNOT do is e.g.
8n - 7 = 7 - 8n
THERE would be a problem.
but again, by also keeping the signs with the terms, it is all OK.
so, yes, we could also do
8n - 7 = -7 + 8n
that is true again.