Question

Which of these proportions could not be used to find x below in the picture?


x/10 =7/4

x/4= 7/10

Answer 1

Geometry's vague, so I'll do my best to explain this...
Somehow, you just have to 'pair corresponding sides'

In particular, the side measuring x (on the bigger triangle)
Which side does it 'jive with' (is similar to) on the smaller triangle?

Answer 2

Well, I asked you a question ^

Which side on the smaller triangle does the x-side on the bigger triangle 'jive with'

By jive, I mean, look similar to.

Sort of like when you zoom in/out.
you can still feel which side is which.