Answer:
-1/2
Step-by-step explanation:
The answer to the question
There are 3 ways of solving a simultaneous problem, substitution method, elimination method and Gauss-Jordan method. I'm gonna use the substitution method since it's easier and i think it would suit your level more.
First let's try solving for y since it's easier to start with.
Firstly we have to find an equation for x:

Great, now we can use the substitution method to find the value of y using the first equation:

Now we know that y=1 we can solve the first equation we made:

And the answer is 
Double check:

And that's our final answer! (4,1)
"One and itself, example would be the least common multiple 2, it would be one and two being they're both multiples of two."
16/80 = 1/5 just put it into the calculator