Question

X(3 - 5) + (4b) =
x = 8 b = 3

Answer 1

x (3-5) + (4b)
= x ( -2) + (4b), since x=8 b=3
= -16 + 12
= -4

What I did there is substitution
Replacing x with 8 ,and b with 3
So -16 is the product of (-2) and 8
And 12 is the product of 4 and 3

FYI: -2 is the result of 3 - 5