Answer:

Step-by-step explanation:




but if

then since


so

or





The reason why the bulletin board notice feel nervous is: it was under a tack
In most common cases, the notice that is putted under a tack is intended to be displayed on the board for a pretty long time, highlighting the importance and the urgeny of the notice.
Answer:
3.5
Step-by-step explanation:
These are similar triangles.
BC:AC = BD:AD
6:5 is the ratio.
Then, simply multiply:
4.2 x 5/6 = 3.5
So, x = 3.5!