Answer:
6m-mn, or 5m-n.
7y+42+5y+30, or 12y+72.
Not sure exactly what you're asking for the third and fourth, but these are the first two simplified.
Assuming you have to create an equation...
s is what you have to figure out so it is the subject of the rule
s=
you now need to find out what to do with the other side
you are taking 50 FROM 80 so
s=80-50
s=30
your answer is 30
We have to basically multiply:

And simplifying that we get

And since there can't be .35 person
So out final answer is