JavaScript (ES6), 28 23 bytes
Saved 3 bytes thanks to @Mukundan314
Expects (A)(n).
A=>n=>eval(A.join`*n+`)
Try it online!
How?
We simply join the input array with "*n+", so that [1,2,3] is turned into "1*n+2*n+3" and evaluate the resulting string.
^ But he gets quite stupid sometimes.
He wrote A=>n=>eval(A.join(`*${n}+`)) without realizing the obvious golf A=>n=>eval(A.join`*n+`)
Call him an "Artificial Idiot".
@Lyxal I think he's definitely written in JavaScript.
JavaScript (ES6), 28 23 bytes
Saved 3 bytes thanks to @Mukundan314
Expects (A)(n).
A=>n=>eval(A.join`*n+`)
Try it online!
How?
We simply join the input array with "*n+", so that [1,2,3] is turned into "1*n+2*n+3" and evaluate the resulting string.
