2/10 + 5/10 = (2+5)/7/10
Or
3/10 + 4/10 = (3+4)/10 = 7/10
You can come up with other ways as long as
a) the numerators add to 7
b) the denominators are both 10
If you want the denominators to be different, then you can have something like
1/5 + 1/2 = 2/10 + 5/10 = 7/10
