36/(13^2 - 11^2) = 36/(13-11)(13+11)=36/2*24=3/4
(26^2 - 12^2)/(54^2-16^2) = (26 - 12)(26+12)/(54-16)(54+16) = 14*38/38*70 =
= 14 /70 = 1/5
(53^2 - 27^2)/(79^2 - 51^2) = (53-27)(53+27)/79-51)(79+51)= 26*80/28*130=4/7
(67^2-17^2)/(83^2-77^2) = (67-17)(67+17)/(83-77)(83+77) = 50*84/6*160=35/8=
=4,375