3/4+1/5=19/20
Multiply 4 by 5 to get a LCD and 20 will be your new denominator,
Multiply the 3 by 5 and put that as the numerator of the new first fraction
(3/4)*5/5=15/20
Multiply the 5 by 4 to get 20 and that will be the denominator of the second fraction, the multiply 1 by 4 and put that over the denominator,
(1/5)*4/4=4/20
Now you can just add across,
15/20+4/20=19/20.