Answer
See the detailed answer below.
Work Step by Step
The first given formula seems to be a net force exerted on an object horizontally. The net force here is zero which means that the object is moving at a constant velocity.
The second formula is the power output of the pushing force.
a) A box of mass 30 kg is pushed by a worker at a constant velocity $v$ in the $x$-direction on a rough surface that has a coefficient of friction between it and the box of 0.20. If you know that the power output of the worker while pushing the box was 75 W, find the box velocity and the magnitude of the pushing force.
b) See the figure below.
c) Solving the first formula for $F_{push}$;
$$F_{push}=0.20\times 30\times 9.8=\color{red}{\bf 58.8}\;\rm N$$
Solving the second formula for $v$;
$$v=\dfrac{75}{F_{push}}=\dfrac{75}{58.8}=\color{red}{\bf 1.27}\;\rm m/s$$
