Answer
$121.7N$
Work Step by Step
$F_G$ of water, tank, and brick is equal to $100N+F_B$ 100 Newtons, mass of water and tank plus the buoyancy force on the brick.
$F_B=\rho_FVg$
$m=\frac{50N}{9.81m/s^2}=5.10kg$
$V=\frac{\rho_B}{m_B}=\frac{5.10kg}{2.3\times10^3kg/m^3}=2.22\times10^{-3}m^3$
$F_B=(1.00\times10^3kg/m^3)(2.22\times10^{-3}m^3)(9.81m/s^2)$$=21.7N$
$F_G=121.7N$
