Question 249947
B = number of boys
G = number of girls
S = number of surfers = 385
.
2/3B + 1/12G = S = 385
.
There are 2 girls for each boy.  
2B = G  .or.
B = 1/2G
.
Substituting into the total equation...
2/3B + 1/12G = 385
.
Multiplying through by 12 to remove the fractions...
8B + G = 4620
.
Substituting for B with 1/2G
8*1/2G + G = 4620
4G + G = 4620
5G = 4620
G = 924
.
Since we know there are twice as many girls as boys,
B = G/2 = 924/2 = 462
.
Now we can check to see if we substitute these value that we find there are 385 surfers...
.
2/3*B = 308
1/12*G = 77
Total=385