question number 7 and 8 pls answer day after tomrrow is my exam

question 7
equation =220 - 3= 217
                313 -3=310
                716-3=713
310/217=1=93
217/93=2=31
93/31=3

713/31=23
HCF= 31


ans:-31


Q8
623-3=620
729-9=720
841-1=840

720/620=1=100
720/100=7=20
100/20=5
840/5=168


HCF=5
Ans=5