Question

Find the measure of angle B
78 degrees
37 degrees
55 degrees
65 degrees

Answer 1

65°

Explanation:

We can apply a theorem known as angle sum property of a triangle,in which all the angles of it sums to 180°,then only it can be a triangle!

In ∆ ABC, by angle sum property,

• <A+<B+<C = 180°

Given that, <A = 2x+4°,

• <B = 2x-9°
• <C = x°

Putting in the values,

• 2x+4+2x-9+x = 180°(Collect terms and solve them)

Solving in the equation,

• 4x-5 +x = 180°(Again collect terms)
• 5x = 185°(Transpose 5 onto RHS)
• x = 185/5 = 37°

We have to find the value of <B:

• 2x-9°

Putting the value of <B:

• 2*37-9
• 74-9 = 65°

Hence the value of <B = 65°