Kevin is 3 times as old as Daniel, 4 years ago, Kevin was 5 times as old as Daniel. How old is Kevin

K = Kevin's age
D = Daniel's age

K = 3D

K - 4 = 5(D - 4)

Plug in 3D for the K values in the second equation.

3D - 4 = 5(D - 4)   Use the Distributive Property
3D - 4 = 5D - 20   Add 4 to both sides
     3D = 5D - 16     Subtract 5D from both sides
    -2D = -16            Divide both sides by -2
       D = 8 
 Now, plug that D value into the original equation.

K = 3D    Plug in the D value
K = 3(8)   Multiply
K = 24

4 years ago, Daniel would've been 4 and Kevin would be 20, so Kevin would've been 5 times as old as Daniel.  And 8 x 3 = 24. Therefore, the answer to your query is that Kevin is 24 years old. Hope this helped and have a great day!