find the magnitude of the sum of these two vectors- 5.00m on A on the line. B 6.00m 30degrees.

Answer 1

Not sure what 5.00m on A on the line means...
anyway, convert A and B from polar to x-y components
add the x- and y- components to produce C = A+B
Then find |C| as usual

Answer 2

If all you mean is that the angle between A and B is 30°, then the law of cosines says that the resultant has magnitude

c^2 = 5^2 + 6^2 - 2*5*6 cos(180°-30°)
c ≈ √113

Answer 3

A+B = 5 + 6[30o] = (5+6*Cos30) + (6*sin30)I = 10.2 + 3i.
A+B = sqrt(10.2^2+3^2) = 10.63 m.