To answer this question you must make a come factor between the 2 fractions I believe the easiest way to do this is multiply the denominator or bottom number by the other one so 4*5 and 5*4 and what you do to the denominator you must do to the numerator so you would have to do 4*4 and 4*5 for the first fraction to get 16/20 and repeat on the other side 1*5 and 4*5 or 5/20 so the to fractions are 16/20+5/20 then add just the numerators 16+5=21 or 21/20 and simplify to 1/20
You can go with any multiple of 3 with the number 3 itself as a pair. So, 3 and 6, 3 and 9, 3 and 12, etc...
The answer to the question
Given:
The three exterior angles of a pentagon measures 60,80 and 90.
To find:
The measure of other two exterior angle, assuming them equally.
Solution:
Let x be the measure of two other exterior angles of the pentagon.
We know that the sum of all exterior angles of a pentagon is 360 degrees.




Divide both sides by 2.


Therefore, the measures of both exterior angles are 65 degrees.