Which is true about y + 3 = 9?
a) y + 3 = 9 is an equation because you can solve for y.
b) y + 3 = 9 is an expression because there is an equal sign.
c) y + 3 = 9 is an equation because y has more than one value.
d) y + 3 = 9 is an expression because it has only one variable