If you subtract one more place, it's almost the same. When a person is not enough, he is the previous one.
68 2 1′ 18″+32 32′28″=(68 +32 )+(2 1'+32')+( 18''+28'')= 100 53'46''
89 -23 12′36″=88 59'60''-23 12′36″=(88 -23 )+(59'- 12')+(60''-36'')=65 47'24''