a)0
b)1
c)128
d)64

Please solve this for me. Need step-by-step explanation. Spam free answer required. Thank you in anticipation.

hope it helps have a great day

Answer is option C

Answer is c) 128

I added the step by step process in the pic attached, I don't know how to explain it very well but you can use binomial theorem for (3x-1)^7

Then you can add up all the coefficients of the calculated values as the question mentions afterwards a^7 + a^6 +..... which means it only wants you to add up the coefficients of the consecutive x terms, otherwise it would say a^7x^7 + a^6x^6 +..... and so on

Hope this helps :)