Answer:
35
Explanation:
so as you can see the little four sided shape is similar to the other shape , it is an enlargement .
so if you divide the same sides the answer would all be the same 
so for this if u divide
 10.5 ÷ 3=3.5
and so is 49÷14=3.5 
and you need to find x÷10=3.5 
so multiply 10 by 3.5 which gives you 35 
hope you understood :)