What is wrong with abbreviating "*y* times 5" as *y5*?

Answer

When multiplying a variable by a number, we write the number first. We could write 5*y* to mean "*y* times 5." We could also write *y* · 5, (*y*)(5), or *y* × 5, but these expressions are all longer than 5*y*. In this instance, shorter is better. No comment.