Here I would use a system of equations. Write out what you know.
Let's use x as the smaller angle and y as the larger one.
We can rearrange the first equation like this
Now we can add the two equations to get this
Divide both sides by two
That means the other angle must be 59 degrees.
Is this the answer we're looking for? 59-31=28 if I am correct in my subtraction.
So we get the answers 31 and 59 by using systems of equations.
I hope I helped