Let’s make Dylan’s age = D, and Billy’s age = B
They say the sum of their ages is 87, which translates to:
D + B = 87
They also say that Dylan is twice as old as Billy, which that translates to:
D = 2B
Now, they want to know Billy’s age, or B, so we’ll substitute out D and we’ll be able to solve out for B
Here’s how we’ll do that:
Because D = 2B, it means that we can simply change the first equation to be:
2B + B = 87, since they told us that D and 2B are the same thing
From there, we add together the Bs:
3B = 87
and divide out the 3 from both sides
B = 29
So, Billy is 29 years old.
And just for more learning, if you wanted to find out how old Dylan is, you’d remember that D = 2B,
and so Dylan is (2x29) 58 years old
