Hector is 12 years old now. In 4 years he will be twice as old as his sister is then. How old will his sister be next year?

Answer 1

H is Hector's age = 12
S is sister's age.
in 4 yrs H will be 16
in 4 yrs S will be S+4
2(S+4) = 16
S =?
Next yrs S will be ?+1

Answer 2

Is it 4 or 8?

Answer 3

Neither.
2(S+4) = 16
2S + 8 = 16
2S = 8
S = 4 is how old the sister is now.
Next year, what the problem asked, sister will be 5.