Answer:
2xy+10z-5yz-4x
Step-by-step explanation:
Just put the positives and negatives together. You can't add or subtract any of them because they aren't like terms.
the height:

(with g being the gravitational acceleration)
First, distribute the 2 across the parenthesis.
10-3v+9v=28
Combine like terms on the left.
10+6v=28
Start to get the numbers on the right and the v alone on the left by moving the 10 to the right.
6v=28-10
6v=18
Divide to get the v alone.
v=3
Hope that helps.