12
That's the equation.
It equals to the equation of a straight line.
y=3
It is an equation and the value of b is 3
12
That's the equation.
an equation 3 + 3 = 6
4
21
no not really
It equals to the equation of a straight line.
y=3
x = 3
It is an equation and the value of b is 3
Without an indication of the equals sign, this is not an equation.
It is an equation in one variable.