As side 7 is to side 5, side 9 is to side x.
Set up a proportion to solve.
7/9=5/x
Cross multiply.
7x=45
Divide both sides by 7
x=6.428=around 6.43
Your answer is C. 6.43 for question 11.
Same thing this time for question 12, set up a proportion.
7/9=x/5
Cross multiply.
35=9x
Divide both sides by 9.
3.888=x=around 3.89
Your answer is C. 3.89 for question 12.
I hope this helps :)