Let there be n problems as that was fed to the computer.

Let t be the time it had taken to solve the first question.

So now according to the problem the time taken to solve the 

successive questions will be t-t/x, t-2t/x,....., t-(n-1)t/x.

There are three variables in the problem - n,t,x.

You need to solve for n.

There are three conditions in the problem. So now use the three conditions and form equations.

Then solve for n.

t-t/x + t-2t/x + t-3t/x + ....... t-(n-1)t/x = 63.5 ----------- (1)

t + t-t/x + t-2t/x +...... + t-(n-2)t/x = 127 ---------- (2)

t-2t/x + t-3t/x + ........ + t-(n-1)t/x = 31.5 --------- (3)

From the three equations, solve for n.

(1)-(3):

t-t/x = 32 ------------- (4)

(2)-(1):

(n-1)t/x = 63.5 ------------(5)

From (2):

(n-1)t - (t/x)(n-2)(n-1)/2 = 127

or (n-1)t*[1 - (n-2)/(2x)] = 127

63.5x*[1 - (n-2)/(2x)] = 127 -------- from (5) (n-1)t = 63.5x

or x[1 - (n-2)/(2x)] = 2

or [2x-n-2] = 4

or x-1 = (n+4)/2 ----------- (6)

Using (4):

(1-1/x)[63.5x/(n-1)] = 32

(x-1)[63.5/(n-1)] = 32 -------- (7)

So 63.5/(n-1) [n+4] = 64

or 63.5(n+4) = 64(n-1)

So 63.5n + 254 = 64n - 64

or 0.5n = 318.

or n = 636.

So 636 Questions would be fed to the computer.