## Basic College Mathematics (9th Edition)

$\angle FRE$ and $\angle FRH$ $\angle ERH$ and $\angle HRG$ $\angle HRG$ and $\angle GRF$ $\angle FRG$ and $\angle FRE$
We know that supplementary angles add up to $180^{o}$. In other words, they form a line. From the figure, we thus have the following supplementary angles: $\angle FRE$ and $\angle FRH$ $\angle ERH$ and $\angle HRG$ $\angle HRG$ and $\angle GRF$ $\angle FRG$ and $\angle FRE$