Answer:
The correct value is t* = 2.797.
Step-by-step explanation:
The first step to solve this problem is finding how many degrees of freedom, we have. This is the sample size subtracted by 1. So
df = 25 - 1 = 24
99% confidence interval
Now, we have to find a value of T, which is found looking at the t table, with 24 degrees of freedom(y-axis) and a two-tailed confidence level of 
. So we have T = 2.797.
First, we subtract 20% of the amount from x, so the initial cost of the furniture should be 80% of x or 0.80x. Then, due to the sales taxs, this amount should be added with 6.25% of itself. Such that,
A = 0.80x + 0.0625(0.80x)
= 0.85x
1)
x+10<-7
bring 10 to the other side
x<-10-7
x<-17
2)
-3x-4>5
bring -4 to the other side
-3x>9
divide -3 at the other side, since it is negative it changes to less than
x<-3
3 6 7 4
+ 6 7 8 9
~~~~~~~
10 4 6 3
