Question

Could someone explain to me how to fine the anwser?

In the figure below, the segment is parallel to one side of the triangle. Find the value of y



9
12
15 3/4
19

Answer 1

have you covered similaritries yet?

Answer 2

Yes, we have.

Answer 3

well, then notice
so, just use proportiions to find "y"

thus \(\cfrac{8+6}{6}=\cfrac{21}{y}\)

Answer 4

How do you know when to add or subtract two numbers over another number?
My online book doesn't explain things very well.

Answer 5

"corresponding" sides

notice, 8+6 is the "left side" of the big one, so, we also use the "left" side of the small one, or 6

then we use the "base or bottom" of the big one, and then we use the base or bottom of the small one :)

corresponding sides