Why is PEMDOS not followed in the following example
Perhaps $4(4y-10)(y+5)/4(y-5)$ means $$ \frac{4\;(4y-10)\;(y+5)}{4\;(y-5)} \tag1$$ I think this is most likely. Or perhaps it means $$ \frac{4\;(4y-10)\;(y+5)}{4}\;(y-5) \tag2$$ I think $(2)$ is less likely. Why? If you really wanted this, then the original would have been written $4(4y-10)(y+5)(y-5)/4$ by a careful mathematician.