Question

identifying an unknown value
what is the value of x?
40
70
140
160

Explanation:

Step1: Identify triangle type

The triangle has two equal sides (marked), so it is isosceles. Equal sides correspond to equal base angles.

Step2: Sum of triangle angles

Sum of angles in a triangle is $180^\circ$. Let the equal base angles be $x^\circ$ each.

Step3: Set up equation

$40^\circ + x^\circ + x^\circ = 180^\circ$ → $40 + 2x = 180$

Step4: Solve for x

$2x = 180 - 40 = 140$ → $x = \frac{140}{2} = 70$

Answer:

B. 70