Answer:
11.95 - 7.95 = 4
4/7.95 = 0.50314465
0.50314465 X 100= 50.314465
50% rounded to 1dp
1, 3, 5, 7, 8, 11, 13, 15 is the answer.
(x-3)^2 + (x+5)^2=9^2
(x^2-6x+9) + (x^2+10x+25)=81
2x^2+4x+34=81
2x^2+4x-47=0
From here just use quadratic formula
is the same as 
Dividing by 3 is the same as multiplying by the fraction 1/3
The t-value measures the size of the difference relative to the variation in your sample data. Put another way, T is simply the calculated difference represented in units of standard error. The greater the magnitude of T, the greater the evidence against the null hypothesis.