AC but is 20 m above the surface of the ocean what is the Evevation

Sea level starts at 0m

Since we start at 0 and it is 20m above sea level, we can add.

0 + 20 = 20m

Therefore, the elevation is 20m

Best of Luck!

I believe the opposite of a number would be the negative of that number. Haven't seen it worded like that before though. Five less is minus 5. Three times the sum is 3(x+(-7)). Is would be equals.

x= a number

Equation:
-x - 5 = 3(x + (-7))

If you solve for x:
-x - 5 = 3(x + (-7))
-x-5=3(x-7)
-x-5= (3*x) + (3*-7)
-x-5= 3x-21
Add -x to both sides
-5= 4x-21
Add 21 to both sides
16= 4x
Divide both sides by 4
4= x

Check:
-x - 5 = 3(x + (-7))
-(4)-5= 3((4) + (-7))
-9 = (3*4) + (-21)
-9 = 12 - 21
-9 = -9

Hope this helps! :)