Question 964489
You need another equation.
You're solving for rate, current, and time but you only have two equations,
{{{(R+W)t=77}}}
{{{(R-W)t=49}}}
You can get, 
{{{Rt=63}}}
and 
{{{Wt=14}}}
But you can't solve for all three. 
Repost if you have additional information.