The formula for electric flux is:

electric flux = E*A (*where E = electric field, A = area)

Furthermore,

E = ke*Q / R^2 (where ke = 8.988*10^9 N*m^2/C^2, Q=charge, R=radius between the charge and point of interest)

A = area of circle = pi*r^2

plugging both of these equations into the formula for electric flux we get:

electric flux = ( ke*Q / R^2 ) * (pi*r^2)

Now you are given that,

Q = 16 µC = 16*10^-6 C

R = 17 cm = 17*10^-2 m

r = 1 mm = 1*10^-3 m

Now plugging these values into the formula for electri flux:

electric flux = (( 8.988*10^9 N*m^2/C^2) * (16*10^-6 C) / (17*10^-2 m)^2 ) * (pi*(1*10^-3 m)^2)

simplify and we get:

electric flux = 15.636 N·m^{2}/C