Question 772699
A data table is not necessary and would be adding more details than we can use.

r = speed of boat if in still water
2 m/s = the given speed of the river's current


r+2 = downstream speed for boat in river
r-2 = upstream speed for boat in river


"twice as fast downstream as upstream":
Means that downstream speed is 2 times the upstream speed.
{{{highlight(r+2=2(r-2))}}}
Algebra steps:
{{{r+2=2r-4}}}
{{{0+2=2r-r-4}}}
{{{2=r-4}}}
{{{r-4=2}}}
{{{r-4+4=2+4}}}
{{{highlight(r=6)}}} {{{m/s}}}, the boat in non-moving water.


Actually, the "speed through the water of the boat" in the two directions are these:
UPSTREAM, {{{r+2=6+2=highlight(8)}}} {{{m/s}}}
DOWNSTREAM, {{{r-2=6-2=highlight(4)}}} {{{m/s}}}