Answer:
d=2
Step-by-step explanation:
We can use the given information to write down two equations that describe the ages of Kevin and Daniel.
Let Kevin's current age be k and Daniel's current age be d.
k=4d
k=d+6
Now we have two independent equations, and we can solve for our two unknowns.
Since we are looking for d, and both of our equations have k alone on one side, this is a convenient time to use elimination.
Subtracting the second equation from the first equation, we get:
0=4d-(d+6)
which combines the information about d from both of our original equations.
Solving for d, we get: 3d = 6.
d=2
