If I had one more sister I would have twice as many sisters as brothers. If I had one more brother I would have the same number of each. How many brothers and sisters do I have?
Three sisters and two brothers.
This can be solved by simple deduction, but if algebra is used let x be the number of sisters and y the number of brothers:
x+ 1= 2y
y+ 1= x
Therefore, y + 1+ 1= 2y
so y =2 or x + 1= 2x – 2
so x = 3.