How to use substitution to solve

Given:
A. Evaluate [tex]\dfrac{3}{8}x-4.5[/tex] when x=0.04.
B. Evaluate [tex]8.4n-3.2p[/tex] when n=2 and p=4.
To find:
The values of the given expression at the given values.
Solution:
A.
We have,
[tex]\dfrac{3}{8}x-4.5[/tex]
Putting x=0.04 in the above expression, we get
[tex]\dfrac{3}{8}(0.04)-4.5[/tex]
[tex]=0.015-4.5[/tex]
[tex]=-4.485[/tex]
Therefore, the value of the expression at x=0.04 is -4.485.
B.
We have,
[tex]8.4n-3.2p[/tex]
Putting n=2 and p=4 in the above expression, we get
[tex]8.4(2)-3.2(4)[/tex]
[tex]=16.8-12.8[/tex]
[tex]=4[/tex]
Therefore, the value of the expression at n=2 and p=4 is 4.