change the fractions ton have the same denmomenator sucha as 4/10 would change as 8/20 because 10x2=20 so 4x2=8. do the same with 2/4 it would cahnge to 10/ 20 cause 4x5=20 so 2x5 =10. when adding then the denimoator 20 will stay the same 20 in the answer and you just have add 8+10=18 so the answer is 18/20
to reduce this fraction you could divied by two, to ge this answer 18 divied by 2 equals 9 and 20 divied by 2 equals 10 , the new answer is 8/10 you can reduce this fraction also by the same way and get 4/5 you can't reduce any more after this fraction so it makes it a reduced fraction