Not so sure.. but I got 9.6 meters below water level.
The solution will be: 
<em><u>Explanation</u></em>
The given inequality is: 
First we will subtract
from both sides. So.....

Now we will subtract 13 from both sides. So.....

Then we need to divide both sides by -3. As here we are <u>dividing the inequality by a negative number, so we need to switch the inequality symbol</u>. So, we will get.......

Thus, the solution will be: 
China plate is 12 years (16-4) and Glass plate is 4 years (12÷3)
Answer:
x=1
Step-by-step explanation:
you would change it to 5x-4(-3x+5)=-3, because you put the info for the first equation into the second equation.
5x-4(-3x+5)=-3
5x+12x-20=-3
17x-20=-3
17x=17
x=1