Can soomeone help me on this one too

70°

Step-by-step explanation:

An euclidean triangle (a triangle on a straight plane) has sum of three angles equal to 180°.

When we talk about a triangle, we usually talk about an euclidean one.

There are also a non-euclidean triangles which are a triangle on circular plane which has sum of angles above 180° and one that is a hyperbolic triangle version which has sum below 180°.

Back to the question, since we know that the triangle is an euclidean one and thus has the sum equal 180°.

x+20+40+2x-30 = 180

Combine like terms:

3x+30=180

Subtract both sides:

3x+30-30=180-30

3x=150

Divide both sides by 3.

3x/3 = 150/3

x = 50

Since we want to find angle B which has measure of 2x-30, substitute x = 50 in 2x-30.

2(50)-30 = 100-30 = 70

Therefore angle B is 70°