We have a known hypotenuse, but unknown opposite side. Use the sine ratio to tie the two together to be able to solve for x.
sin(angle) = opposite/hypotenuse
sin(50) = x/6.5
6.5*sin(50) = x
x = 6.5*sin(50)
x = 4.97928888027336 make sure your calculator is in degree mode
x = 4.98
Answer is choice B