Writing algebraic subtraction expressions | 6th grade | Khan Academy

We have different statements here that can each be expressed as an algebraic expression. As you might have guessed, I would love you to pause this video and try to write each of these statements as an algebraic expression before we do it together.

All right, now let's work on it together. So this first statement we have: "2 less than x." My brain thinks, all right, let me start with x. How am I going to get 2 less than that? Well, I'm going to subtract 2.

This is an interesting example because you see the order that we see it in the sentence is not the order that we would necessarily write it in the expression. Right over here, it’s very important to think about what is going on here: what is being described?

Now, this next statement: "y fewer than three." Well, in my mind, I'm going to start with three, and I'm going to be y fewer than that. So, I'm going to start with 3 and then I'm going to be y fewer than that.

Now, these first two statements are similar in that you have something less than something else or something fewer than something else. They just swapped the number and the variable.

Now, this third statement: "x decreased by five." So, my mind is thinking, what am I starting with? I'm starting with an x, and I'm decreasing it by five. So, I could view that as minus 5, or I'm going to take a 5 away from it.