I am confused with this

Question

Jeremy is twice as old Randy now. 6 years ago, the sum of their age was 18. How old is Jeremy now?

Answer 1

J=2R

J-6 + R-6 = 18

J+R =18+6+6

2R +R = 30

3R=30

R =30/3 =10 = Randy's age now

J=20 = Jeremy's age now

6 years ago they were 4 and 14 which sums to 18