Question

Using the following diagram, solve for x.

Answer 1

The answer to this equation is x=63

Answer 2

Answer:

$x=10.5$

Step-by-step explanation:

Use Thales' Theorem which says: If two lines, not necessarily parallel, are cut by a system of parallel lines, then the segments that result on one of the two lines are proportional to the corresponding segments obtained on the other.

Take a look at the picture I attached you, from it, It is true that:

$\frac{AB}{A'B'} =\frac{BC}{B'C'}$

Hence:

$\frac{12}{6} =\frac{21}{x}$

Solving for x:

$x=\frac{21}{2} =10.5$