The axis of symmetry for the graph of the function f(x) = 3x2 + bx + 4 is x = 3/2 . what is the value of b?

The axis of symmety is the x value of the vertex

to find the x value of the vertex of ax^2+bx+c=0
x value=-b/2a

3x^2+bx+4=0
3/2=vertex

-b/2(3)=3/2
-b/6=3/2
times 6
-b=18/2
-b=9
times -1
b=-9

Letter c i’d say

The answer is $9.90 with rounding to the nearest tenth