If we know that b(b^4 * b^3)^2 = b^3x for all real numbers b, what is the value of x?

b ( b^4 * b^3)^2  =  b^(3x)

b ( b^7)^2   = b^(3x)

b (b^14)  =  b^(3x)

b^15  =  b^3x

15 = 3x

x  = 15 /  3  =   5