I hope this is not last minute work for the holidays 🙂

12.

Let B be cost of blouse.
Let T be cost of t-shirt.  T = B-15
Let S be cost of skirt. S = B+9

So, 2B + 3T + 2S = 267
=> 2B + 3(B-15) + 2(B+9) = 267
=> 2B + 3B – 45 + 2B + 18 = 267
=> 7B – 27 = 267
=> 7B = 267 + 27 = 294
=> B = 294/7 = $42 #

13.

(1) E + M = 175
(2) E + S = 164
(3) M = E – 11

Substituting (3) into (1)
E + (E – 11) = 175
2E = 175 + 11 = 186
E = 93

So, in (2), we get
E + S = 164
=> 93 + S = 164
=> S = 164 – 93 = 71 #

14.

3T + 5(T-5) = 87
3T + 5T – 25 = 87
8T = 87 + 25 = 112
T = 14 #

15. 

Let P be the cost of a pot.
Let L be the cost of a plate.

(1) P + 9L = 78

But (2) P = 4L

Substituting (2) into (1),
4L + 9L = 78
13L = 78
L = 6
So (2) gives P = 4L = 24

So cost of 2 pots and 1 plate is: 2P + L = 2(24) + 6 = $54 #