The letter "x" is often used in algebra to mean a value that is not yet known. It is called a "variable" or sometimes an "unknown". In x + 2 = 7, x is a variable, but we can work out its value if we try!
Hope this helps
Y=3x-2 is parallel to line a(have the same slope)
y=-1/3x-10 is perpendicular
y=1/3x+1 is not parallel nor perpindicular
You have to divide 140,000 by 7 to get the base number of 20,000. You then multiply it by 2 and 5 for each respective person. Joe invested 40,000 and Matt invested 100,000.
Product one because it will increase exponentialy