The following sulphur isotopic data were obtained for a sulphide ore in mexico.

sample 

34s galena (ga) ‰ 

34 s sphalerite (sp) ‰ t in c

1 -1.15 +0.95

2 -1.11 +0.87

3 -1.42 +1.03

4 -1.71 +0.01

the fractionation, sp-ga, between sphalerite and galena has been found to vary with temperature as:

6

2

sp 1.02 10

ga

x

t

 =

a. calculate the temperature in c at which each mineral pair equilibrated and fill the results in the

table above! (show one example of the calculation procedure here! )

Mrs. julien’s and mrs. castillejo’s classes are selling cookie dough for a school fundraiser. customers can buy packages of macadamia nut chip cookie dough and packages of triple chocolate cookie dough. mrs. julien’s class sold 25 packages of macadamia nut chip cookie dough and 30 packages of triple chocolate cookie dough for a total of $221.25. mrs. castillejo’s class sold 5 packages of macadamia nut chip cookie dough and 45 packages of triple chocolate cookie dough for a total of $191.25. (a) write the system of equations that model the problem. be sure to explain which equation represents which situation. (b) find the cost of each type of cookie. show your work. (c) explain which method you used to solve the system and why you chose that method.