Question

What should we add to 12 2/15 to get 18 9/25 ?

Answer 1

12 2/15=12*15+2/15=182/15
18 9/25=18*25+9/25=459/25
182/15+x=459/25
x=459/25-182/15
LCM of 25 and 15 is 75
so
x=459*3/75-182*5/75
x=1377/75-910/75
x=467/75


so we should add 467/75 to 12 2/15 to get 18 9/25.