Which of these is an equation?

a
9x - 7

b
(b + 7) x 3

c
4x + 9 = 45

d
(⅔)x - 3 > c

Pls . yeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeet

If the measure of xyz is 81 what is the measure of yz

What is the domain and range of each function 1. x (3, 5, 7, 8, 11) y ( 6, 7, 7, 9, 14) 2. x (-3, -1, 2, 5, 7) y (9, 5, 4, -5, -7)