If one-third of the girls and one-half of the boys attend the Senior Dance, there will be a total of 205 students. If half the girls and all the boys attend, there will be 370 students.

How many students are in the Senior class?

g/3 +b/2 =205

g/2 + b = 370

2g/3 +b =410
g/2 + b = 370

4g/6 +b =410
3g/6 + b = 370
------------------------ subtract
g/6 = 40
g = 240
b = 370 - 120 = 250
g + b = 490 ?