77°24′+34°40′=112°04‘
108°18′-56°21′=51°57
15°36′18″×2=31°2’36”
109°23′18″÷3=36°27‘46“过程~~77°24′+34°40′=77°+34°+24‘+40’=111°+64‘=11°+1°4’=112°4‘108°18′-56°21′=107°+1°18‘-56°-21’=51°+78‘-21’=51°+57‘=51°57’15°36′18″×2=15°×2+36‘×2+18“×2=30°+72’+36”=30°+1°12‘+36“ =31°2’36”109°23′18″÷3=108°÷3+1°23’18”÷3=36°+81‘÷3+138”÷3=36°+27‘+46“=36°27‘46“