Answer: The critical value for a two-tailed t-test = 2.056
The critical value for a one-tailed t-test = 1.706
Step-by-step explanation:
Given : Degree of freedom : df= 26
Significance level : 
Using student's t distribution table , the critical value for a two-tailed t-test will be :-

The critical value for a two-tailed t-test = 2.056
Again, Using student's t distribution table , the critical value for a one-tailed t-test will be :-

The critical value for a one-tailed t-test = 1.706
Answer:
Original number = 38
Step-by-step explanation:
10*x + y
x = y - 5
10y + x = 2 (10x + y) + 7
10y + y - 5 = 2(10(y - 5) + y) + 7
11y - 5 = 2(10y - 50 + y ) + 7
11y - 5 = 2(11y - 50) + 7
11y - 5 = 22y - 100 + 7
11y - 5 = 22y - 93
11y + 88 = 22y
88 = 11y
y = 8
x = y - 5
x = 8 - 5
x = 3
So the original number is 38. Does that work?
3 is 5 less than 8.
83 = 2*38 + 7
83 = 76 + 7
83 = 83. Yes it works.
I don't know if this is right but 0.125