You could solve it with this equation; 3x + x = 24
Let 3x = Juan's age
let x = Carmen's age
Now lets solve their ages!
3x + x = 24
4x = 24 (combined liked terms)
x = 24 ÷ 4
x = 6
So Carmen's age is...6
Now lets substitute the value of x in the original equation to find Juan's age;
3x + x = 24
3(6) + (6) = 24
(3 × 6)+ 6 = 24
(18) + 6 = 24
24 = 24
So Juan's age is...18
Lets check if their ages add up to 24;
18 + 6 = 24
24 = 24
So their ages are correct! Hope this helps you! :D