Apply the remainder theorem:
The remainder of dividing of a polynomial P(x) (ANY POLYNOMIAL !!) by the binomial (x-a) is equal
to the value P(a) of the polynomial at x= a.
And you will get for your case
3^3 - a*3^2 - 5*3 + 4 = 97. (1)
It is your equation to determine the value of "a".
Now you can complete the assignment on your own, by finding "a" from the equation (1).
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On the Remainder theorem, see my lessons in this site