Python 3 - 318

Note: Due to parsing difficulties, there are no fractions with the number 0 in (so no fractions are calculated using the correct method).

n=int(input());s=str;r=range
print([[a,b] for a in r(1,n) for b in r(1,a) for i in r(1,n) if i!=a and i!=b and s(i) in s(a) and s(i) in s(b) and s(a).count(s(i))<len(s(a)) and s(b).count(s(i))<len(s(b)) and not '0' in s(a) and not '0' in s(b) and eval(s(a).replace(s(i),'')+'/'+s(b).replace(s(i),''))==a/b and a+b<=n])

With n=80:

[[64, 16]]

With n=147

[[64, 16], [65, 26], [95, 19], [98, 49]]

With n=500

[[64, 16], [65, 26], [95, 19], [98, 49], [136, 34], [192, 96], [194, 97], [195, 39], [196, 49], [196, 98], [231, 132], [238, 34], [238, 136], [242, 143], [253, 154], [264, 165], [268, 67], [275, 176], [286, 187], [291, 97], [291, 194], [294, 49], [294, 98], [294, 196], [295, 59], [297, 198], [298, 149], [325, 13], [341, 143], [345, 138], [392, 49], [392, 98], [395, 79]]