If `^12P_r-118800`, find r.

If ^20P_r=6840 , find r.

(i) If ""^(5)P_(r)=2xx""^(6)P_(r-1) , find r. (ii) If ""^(20)P_(r)=13xx""^(20)P_(r-1) , find r. (iii) If ""^(11)P_(r)=""^(12)P_(r-1) , find r.

If ^(10)P_(r)=5040, find the value of r

(i) If ""^(15)P_(r)=2730, find the value of r. (ii) If ""^(10)P_(r)=5040, find the value of r.

If ""^(22)P_(r+1):""^(20)P_(r+2)=11:52, find r.

If ""^(10)P_(r) = 720, find r.

If 22P_(r+1):^(20)P_(r+2)=11:52, find r

If 7. ""^5p_r = ""^7p_(r-1), then find r.

If P(5,r)=2,P(6,r-1), find r

(a) If .^(22)P_(r+1):^(20)P_(r+2)=11 : 52 , find r. (b) If .^(56)P_(r+6):^(54)P_(r+3)=30800: 1 , find r.