We can find the y-component of the resultant force by adding the y-components of the two 20N forces.
For a force of magnitude F and lying at an angle off the x-axis θ, the y-component of the force is given by:
Fsin(θ)
The magnitude of the two forces is 20N, and they lie at 30° and 60°, so the sum of their y-components, and therefore the y-component of the resultant force, is:
20sin(30°)+20sin(60°)
= 27.3N
