In order for a field trip to be scheduled, at least 30 students must sign up. So far, 23 have signed up. At least how many more students must sign up in order for the field trip to be scheduled?

7

There's a trip coming up and 30 students need to sign up for it to be a go. So let's write down 30.

30

We already have 23 signed up. So let's write that down too:

23

Ok - now I'm going to compare them - on one side will be Have and on the other will be Need:

##Have=Need##

##23=30##

Ok - do they really equal each other yet? No - they don't. The left side, the Have side, needs more people. How many more people do we need to add? Let's first make a space to put the number in (and I'll use an ##x## to hold the space):

##23+x=30##

So we're saying that we Have 23 people and need x people more to get to 30 - the number we Need in order for the trip to happen.

At this point, you might just look at this and know that we need 7 more people and you'd be right. But I'm going to take the extra step of actually solving for x. I'm going to do that by subtracting 23 from both sides of the equation:

##23+x-23=30-23##

##x=7##