You purchase a total of 45 shares of stocks from 3 different companies. you purchase twice as many shares of company c stock as you do company a. company a stock sells for $15, company b sells for $12, and company c sells for $18.
a) define a single variable and write an equation for the total cost of the stock
b) if you bought 10 shares of company a stock, what was the cost
c) six months later the value of company a's stock increased 25%, and company c's decreased 10%. write a new equation to express the value of the stock now.
d) what is the percent of increase or decrease in the value of your purchase from part b?

A)The total cost would be: x=15a+12b+18c where x is the total cost and a,b,and c are the amount of stocks you bought from their respective companies.

B) Since you bought 10 A stocks, you must have bought 20 C stocks. That adds up to 30 bought, leaving 15 for B.

x=(15)(10)+(12)(15)+(18)(20)
x=150+180+360=$690 spent

C) A's stock is now 15(1.25) which is 18.75. C's stock is now 18(.90) which is 16.2
new equation is 18.75a+12b+16.2c=x

D) Substitute the number of stocks we bought from each in again:
187.5+180+324=$691.5

The cost went up slightly, so divide 690/691.5 then multiply that number by one hundred. You get that you spent in B 99.8% the amount you spent in C. So 100-99.8= an increase of .2% 

Yes i also think it is b