You received a ​$150 gift certificate to a clothing store. The store sells​ T-shirts for ​$17 and dress shirts for ​$26. You want to spend no more than the amount of the gift certificate. You want to leave at most ​$8 of the gift certificate unspent. You need at least two dress shirts. What are all of the possible combinations of​ T-shirts and dress shirts you could​ buy?

Let's solve this problem step by step:

1) We know that we want to spend no more than the amount of the gift certificate, which is $150. Therefore, we can form a basic equation: 17T + 26D ≤ 150, where T represents the number of T-shirts and D represents the number of dress shirts.
2) We also want to leave at most $8 of the gift certificate unspent. This means that 17T + 26D ≥ 142.
3) Since we need at least two dress shirts, the minimum value for D is 2.
4) Now we can start determining the combinations:
a) Let's start by plugging in D = 2 into the equation: 17T + 26(2) ≤ 150
Simplifying this, we get: 17T + 52 ≤ 150
Subtracting 52 from both sides: 17T ≤ 98
Dividing by 17: T ≤ 5.764
Since the number of T-shirts must be a whole number, the maximum value for T in this case is 5.
Therefore, we have the first combination: T-shirt = 5, Dress shirt = 2

b) Plugging in D = 3 into the equation: 17T + 26(3) ≤ 150
Simplifying this, we get: 17T + 78 ≤ 150
Subtracting 78 from both sides: 17T ≤ 72
Dividing by 17: T ≤ 4.235
The maximum value for T in this case is 4.
So, we have the second combination: T-shirt = 4, Dress shirt = 3

c) Plugging in D = 4 into the equation: 17T + 26(4) ≤ 150
Simplifying this, we get: 17T + 104 ≤ 150
Subtracting 104 from both sides: 17T ≤ 46
Dividing by 17: T ≤ 2.764
The maximum value for T in this case is 2.
So, we have the third combination: T-shirt = 2, Dress shirt = 4

d) Plugging in D = 5 into the equation: 17T + 26(5) ≤ 150
Simplifying this, we get: 17T + 130 ≤ 150
Subtracting 130 from both sides: 17T ≤ 20
Dividing by 17: T ≤ 1.176
The maximum value for T in this case is 1.
So, we have the fourth combination: T-shirt = 1, Dress shirt = 5

Therefore, all possible combinations of T-shirts and dress shirts that can be bought are:
1) T-shirt = 5, Dress shirt = 2
2) T-shirt = 4, Dress shirt = 3
3) T-shirt = 2, Dress shirt = 4
4) T-shirt = 1, Dress shirt = 5