In order to combine like terms, they must share the same variable. We can't combine things 9y and 3p because they contain two different variables. On the other hand, 7r and r work because there is only one. 7r and r combine to 8r+2
it's d because if 74 would be the same as the left side next to x and if you turn that into a problem like 180-74 and I got 180 cause half of a circle is 180 and then my answer would be 106 I'm not good at explaining but it's d
