If `a ,b ,c ,d ,e ,f` are A.M.s between 2 and 12, then find the sum `a+b+c+d+e+fdot`

If a ,b ,c ,d ,e are in A.P., the find the value of a-4b+6c-4d+edot

Given a ,b ,c are in A.P. b ,c , d are in G.P. and c ,d ,e are in H.P. If a=2and e=18 , then the sum of all possible value of c is ________.

a , b , c , d are in increasing G.P. If the AM between a and b is 6 and the AM between c and d is 54 , then the AM of a and b is