To answer this question, simply plug in the values that represent the variables into the respective equations.
If z=5 and y =3, then 12z - 3y can be written as:
(12 × 5) - (3 × 3)
(60) - (9)
= 51
If z = 5, then the expression 4z -z can be written as:
(4 × 5) - 5
20-5
= 15
51 and 15 are your answers