Remember
we can do anything to an equation as long as we do it to both sides
try to isolate the variable
you have 2 types
x+b=c
x/b=c
fior the first type, minus b from both sides to get
x=c-b
for the second, multiply both sides by b to get rid of the fraction to get
x=cb
also remember that -x times -1=x
b.add 25 to both sides
-a=20
multiply -1
a=-20
c.
-t/8=-4
multiply both sides by 8
-t=-32
mutiply -1
t=32
d. -n/-5=-30
mulitply both sides by -5
-n=150
multiply both sides by -1
n=-150
e. multiply both sides by 12
-l=144
multiply b y-1
l=-144
Answer:
={6,7,8,9,10}.
Step-by-step explanation:
We have an empty set: M={} and the set N={6,7,8,9,10}.
The union of these two sets are elements in M or N or both.
Since the M is a null set, 
Therefore:
={6,7,8,9,10}.
The union for the given sets is {6,7,8,9,10}.
35% of 80 is 28.
80 x 0.35 = 28
I hope this helps.