Answer:
CB is 8.8 ⇒ D
Step-by-step explanation:
In any triangle, the line segment joining the mid-points of two sides is parallel to the 3rd side and equal to half its length
In the given figure
∵ ABC is a triangle
∵ E and D are the midpoints of sides AC and AB
∵ CB is the 3rd side
→ By using the rule above
∴ ED // CB
∴ ED = [tex]\frac{1}{2}[/tex] CB
∵ ED = x + 0.7
∵ CB = 3x - 2.3
→ Substitute them in the equation above
∴ x + 0.7 = [tex]\frac{1}{2}[/tex] (3x - 2.3)
∴ x + 0.7 = [tex]\frac{1}{2}[/tex] (3x) - [tex]\frac{1}{2}[/tex] (2.3)
∴ x + 0.7 = 1.5x - 1.15
→ Subtract 1.5x from both sides
∵ x - 1.5x + 0.7 = 1.5x - 1.5x -1.15
∴ -0.5x + 0.7 = -1.15
→ Subtract 0.7 from both sides
∵ -0.5x + 0.7 - 0.7 = -1.15 - 0.7
∴ -0.5x = -1.85
→ Divide both sides by -0.5
∴ x = 3.7
→ Substitute x by 3.7 in the expression of CB
∵ CB = 3(3.7) - 2.3
∴ CB = 11.1 - 2.3
∴ CB = 8.8
