Answer: 10
Concept:
Here, we need to understand the idea of evaluation.
When encountering questions that gave you an expression with variables, then stated: "If x = a, y = b, z = c" (a, b, c are all constants), this means you should substitute the value given for each variable back to the expression.
Solve:
**Disclaimer** I assumed that the [1/2] in [1/2ac2] is a single term and [c2] in [1/2ac2] is b². If it was, then you may refer to my answer. If it was not, then you may tell me and I will redo it.
Given information
a = 5
b = 2
Given expression
(1/2) · a · b²
Substitute values into the expression
=(1/2) · (5) · (2)²
Simplify exponents
=(1/2) · (5) · (4)
Simplify by multiplication
=(2) · (5)
=10
Hope this helps!! :)
Please let me know if you have any questions