You can just use basic trigonometry to solve for the x & y components.
vector a = 10cos(30) i + 10sin(30) j = <5sqrt(3), 5>
vector b is only slightly harder because the angle is relative to vector a, and not the positive x-axis. Anyway, this just makes vector b with an angle of 135deg to the positive x-axis.
vector b = 10cos(135) i + 10sin(135) j = <-5sqrt(2), 5sqrt(2)>
So now we can do the questions:
r = a + b
r = <5sqrt(3)-5sqrt(2), 5+5sqrt(2)>
(a) 5sqrt(3)-5sqrt(2)
(b) 5+5sqrt(2)
(c)
|r| = sqrt( (5sqrt(3)-5sqrt(2))2 + (5+5sqrt(2))2 )
= 12.175
(d)
θ = tan-1 ( (5+5sqrt(2)) / (5sqrt(3)-5sqrt(2)) )
θ = 82.5deg