Fred is 4 times as old as his niece Selma. In ten years, he will be twice as old as she will be. How old is each now?

Question

I'm am confused on how you make the equation 

Answer 1

Translate the words into equations:

 

F = 4S

F+10 = 2(S + 10)

 

Substituting F in the first equation:

 

4S + 10 = 2S + 20

2S = 10

S = 5

 

Then Fred is 20 now and Selma is 5 and in ten years they will be 30 and 15.