Question 221560
The question is: 
A class of Math A30 students contains twice as many girls as boys. Last Friday, 
Equation: 
g = 2b
--------------------------------
when two of the boys were absent and all the girls were there, the number of girls tripled the number of boys.
Equation:
g = 3(b-2) 
 

How many boys and how many girls are in the class?
Substitute for "g" and solve for "b":
2b = 3b-6
b = 6 (# of boys before 2 were absent)
---
Since g = 3(b-2), g = 3(6-2) = 12 (# of girls)
==================================================
Cheers,
Stan H. 
----------------------------------------------