So you question is most likely about a triangle DEF with the 3 angles being named D, E, F. The triangle would look something like the image attached below.
If that is what is being asked then i need more info to answer but
By Definition it would be 180 degrees.
A proportion looks like this:

It means that the quantity a,b,c and d are in the same proportion: the ratio between a and b is the same ratio between c and d.
They are particularly useful in situation when you have an example given, and you want to extrapolate the relationship for another couple.
For example, you can think of the following problem: "Five apples cost 2 dollars. How much will 8 apples cost?"
You can build the proportion

And then solve it for x:

Answer:
type of angles is complementary
equation is (3x-5)+x=90
x=23.75
Answer:
2x + 3y=-10 is incorrect (I think)
When you mulitply something with no negative you get something with no negative
Hope this helps :)
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