A boat is moving at 3m per second as it approaches a bridge.Aperson drops a package from the bridge

well its not so  complicated, here we shall  use the concept that the   time taken by pacakage  to travell vertical distance is equal to the time taken by the  boat to  just reach beneath the bridge.

Now time taken by the pacakage can be calculate  by applying equation of motion

here initial velocity is zero, so h=(1/2)gt² from here we can calculate the time taken by the package.

now till  the package reaches just beneath the bridge, then boat will arrive there

so we can calculate the time taken by the package from above equation.

then distance travelled by the boat we can calculate as distance= speed  multiply by time. and the value of time can be calculated from the above equation.

i hope you understood.