Solve by finding a common denominator 3/4+1/5 the common denominator is 20 but how do you find the top number?

The fractions are 15/20 and 4/20

Step-by-step explanation:

3/4 + 1/5 = 19/20

For example, if you have the fraction 3/4 you would multiply the demominator  by 5 to get 20. What you do to the denominator, you have to do to the top (the numerator). Since you multiplied the denominator, 4, by 5 you have 20. Now you have to multiple the numerator by 5, which gives you 15 because 3 x 5= 15. Your final fraction should be 15/20

Do this process to the 1/5 fraction:

1/5

Multiply 5 x 4 to give you 20 since 20 is the common denominator. Now, you have to multiply the numerator, 1, by 4. Whatever you do to the bottom, you do to the top. 1 x 4= 4. Your final fraction should be 4/20

Now sum the fractions up:

15/20 + 4/20 = 19/20