Answer:
Let Luke be represented as L , rachel be represented as R and daniel be represented as D
As per the statement: Luke has $21 more than rachel and $48 more than daniel
⇒
and L = 48+D
equate these two we get;
21 + R = 48 + D
we can write this as;
R = 48+D -21
R = 27 +D ......[1]
Also, it is given that altogether they have $168.
⇒
.....[2]
Substitute the value of L=21+R in equation [2] we have;

Combine like terms;

Subtract 21 from both sides we get;
2R+D= 147 ......[3]
Substitute the value of equation [1] in [3] we get;
2(27+D)+D = 147
Using distributive property;

54 + 2D +D = 147
Combine like terms;
54 +3D =147
Subtract 54 from both sides we get;
3D = 93
Divide both sides by 3 we get;
D = $31
Now, substitute this value of D in L = 48+D we have;
L = 48 + 31 = $79
Therefore, $79 does Luke have.