First, find the least common denominator, which in this case is 20. Then, multiply the numerator the same amount of times that you did the denominator, which is 5 and 4, respectively, which equals 5 and 8, respectively. Then, add the numerators, which equals 13. So, 13/20 is your final answer.
In order to solve this,we need to make sure that the denominators are the same. We can do this by finding the lowest common denominator, meaning which number in the denominator when multiplied by 1,2,3,4 etc will give us the lowest possible number. In this case it is 20. Since we are changing the denominator we have to multiply the numerator and denominator of 1/4 by 5 which gives us 5/20, and we need to multiply the numerator and denominator of 2/5 by 4, giving us 8/20
Now we just the numerators of the two fractions which gives us the answer of 13/20
