First bring them to common denominator.
Here, I'll do the first one for you.
When they are talking about a number, use "x".
Since it says twice a number, you say 2x. Or 3x for three times the number
2x+12=3x-31
Then use algebra to find x. Get the numbers on one side and all the x's on the other.
2x+12+31=3x-31+31
2x+43-2x=3x-2x
x=43
Now do the rest on your own!
she went down the slope 10.2 meters, -10.2
then she jumped down to the lake 1.5 meters, -1.5
-10.2 - 1.5 = -11.7 meters.
so she pretty much went 11.7 meters down from her original location.
