For addition of these two quantities we just need to equalize the denominator first then we have to add them. We don’t need to do any application with the numerator. For equalizing the denominator we need to follow some specific rules:

We have to multiply both the denominator and numerator with the same integer so the value of fraction doesn’t change and we have to multiply the integer in a manner so that the value of both the denominator will be same or for simplification you can multiply the first value by denominator of second and second value with the denominator of first. Now, let’s see how to multiply 3*5/4*5+4*4/5* 4, the denominator of first number is 4 and we have multiply it on both the numerator and denominator. The denominator of second number is 5 and we have multiplied it on both the numerator and denominator. Now, the result will be:
 
15/20 +16/20,
 
Now it’s very easy we just have to add the numerator denominator remains the same so, required answer will be:
 
15/20 + 16/20=31/20.