Each of my daughters has as many brothers as sisters, but each of my sons has three times as many sisters as brothers. how many children do i have?

 Lets assume number of daughters = x 
and number of sons = y 

each daughter has as many sisters as brothers so, 
y = x - 1 
x - y = 1 (1) 

each son has 3 times as many sisters as brothers so, 
x =3(y - 1) 
x = 3y - 3 
x - 3y = -3 (2) 

Subtract (2) from (1), 
-y + 3y = 1 - (-3) 
2y = 4 
y = 4/2 = 2 

From (1), 
x - y = 1 
x - 2 = 1 
x = 1 + 2 = 3 

Daughters = x = 3 
Sons = y = 2 
Total children = 2 + 3 = 5