First add 7d to both sides:
-22 = 11d
Now divide by 11 both sides
-2 = d
You can work on either side of the equation, I used the right side for the variables because it was easier to add to positive numbers than dealing with negative numbers on the left side:
-7d -4d = 22
-11d =22
d = -2
either way you get the same answer :)
Answer:
Step-by-step explanation:
The total number of ways of selecting 3 gems of any kind without replacement is 35 * 34 * 33 = 39270
Now selecting 2 gems from 25 is 25C2
25 C 2 = 25 * 24/2 = 300
Selecting one good gem is 10
Total selection = 300 * 10 = 3000
P(gems) = 3000 / 39270
P(gems) = 300/3927
P(gems) = 100/1309
$249.......................................