how do you get the answer for 1/2 - 7/10 =

to get the answer for 1/2-7/10 you must have both of the bottom numbers be equal multiply 2 and 1 by 5 to make it 5/10  5/10-7/10= -2/10 which is 1/5 correct answer is -1/5

The girl or boy above me said the correct answer but if you wanted to do 7/19 - 1/2 that's a different story