Question

in an arithmetic progressions if sum of x th term is equal to 7x square - 8x then 10th term is

Answer 1

"sum of the xth term" makes no sense. If you mean

"sum of the first x terms", then
x/2 (2a+(x-1)d) = 7x^2 - 8x
so d = (14x^2 - (2a+16)x)/(x-1)
or, a = (7x-8)/(x-1)d
Now evaluate a+9d
Somehow I think you've garbled the question.