**Solution:**

To find the magnitude of force 2, we can use the concept of vector addition. The resultant of two forces is given by the vector sum of the two forces. Let's break down the problem step by step.

**Step 1:**
Given that the magnitude of the resultant force is 20N. Let's denote the magnitude of force 1 as F1 and the magnitude of force 2 as F2.

**Step 2:**
We are also given that the magnitude of force 1 is 20×√3 N and it makes an angle of 30 degrees with the resultant. Let's denote the angle between force 1 and the resultant as θ1.

**Step 3:**
Since we know the magnitude of force 1 and the angle it makes with the resultant, we can use trigonometry to find the horizontal and vertical components of force 1. The horizontal component (F1x) can be calculated as F1 * cos(θ1) and the vertical component (F1y) can be calculated as F1 * sin(θ1).

**Step 4:**
Now, let's consider force 2. Since we don't have any information about the magnitude or angle of force 2, let's denote the angle between force 2 and the resultant as θ2.

**Step 5:**
We can express force 2 in terms of its horizontal and vertical components. Let's denote the horizontal component of force 2 as F2x and the vertical component of force 2 as F2y.

**Step 6:**
Since the resultant of the two forces is given by their vector sum, we can write the following equations:

F1x + F2x = 0 (The horizontal components of the forces add up to zero)
F1y + F2y = 20 (The vertical components of the forces add up to the magnitude of the resultant force)

**Step 7:**
We can solve these equations to find the values of F2x and F2y. Once we have the values of F2x and F2y, we can use the Pythagorean theorem to find the magnitude of force 2. The magnitude of force 2 can be calculated as √(F2x^2 + F2y^2).

By following these steps, we can determine the magnitude of force 2 and solve the problem.

Magnitude of F2 is 10