My brother is 4 times as old as I am. Six years from now, he will be twice as old as I will be. How old is my brother now?

Let my present age be x.

My brother is 4 times as old = 4*x = 4x

Six years from now:

My age would be x + 6

Brother's age would be: 4x + 6

Brother would be twice my age.

4x + 6 = 2 * (x + 6)

4x + 6 = 2*x + 2*6

4x + 6 = 2x + 12

4x - 2x = 12 - 6

2x = 6

x = 6 / 2

x = 3

Age of brother = 4x = 4*3 = 12

Brother = 12 years old now.

Hope this explains it.

Let, the present age of yours = x

present age of your brother = 4x

After 6 years, 2 (x+6) = 4x+6

2x+12=4x+6

2x=6

x=3, 4x=12

So, your brother is 12 years of age now.