15a =6a - 90
Move all the numbers with variables to one side
15a - (6a) = 6a -(6a) -90
9a = -90
9a/9 = -90/9
a = -9
Hope this helps
y=mx+b plus in slope and you get your answer
Answer: B. 
Step-by-step explanation:
The notation to express a dependent variable is given by :-
, where Y is depending variable which is dependent upon x ( independent variable).
The given statement : The distance an airplane travels depends on how much time it spends flying.
Here , Independent variable : Time
Dependent variable : Distance
Then , the notation to express distance (dependent variable) the airplane flies in 20 minutes is given by :-

In geometry, the circumference (from Latin circumferences, meaning "carrying around") of a circle is the (linear) distance around it. That is, the circumference would be the length of the circle The area of a circle is pi (approximately 3.14) times the radius of the circle squared.
Answer:
m=2
Step-by-step explanation:
STEP 1 : m+0.6=2.6
move constant to the right-hand side and change it's sign m=2.6-0.6
STEP 1: m=2.6-0.6
subtract the numbers m=2