Y2-y1/x2-x1 then plug in numbers so 6-2/10-1 which gives 4/9
The mistake made by student is 6x(3) = 18x
because 18x + 6x = (18+6) x = 24x
You just multiply the numerators of the fractions and the denominators of the fractions together, and then reduce the fraction to simplify it from that point on.
Solution here,
In the figure, the upper small triangle is similar to a lagre triangle.
Now, from the property of similar triangle,

therefore, x= 7