The two graphs in D are not inverses of each other.
If mark and 8 of his friends went out the total of people is 9, so if you think about it 9x9=81 so the total cost of the bill was $81
The coordinates of the vertices of the parallelogram, given that s is a units from the origin, Z is b units from the origin, and then length of the base is c units could be the following:
W(b+c, 0), Z(b, 0), S(0, a), T(c,a)
root 30 ..................
I’d say -1 but you probably need a better answer so I’d say -2.5
