Could you help me on number 4 of page 69 please? I forgot how to set up the equation

Sure. Here’s the question:

To write the equations, let’s say that c is the number of campers. The question gives us n for the number of lollipops.

“…if she were to give each camper 7 lollipops, she would have 10 left over”

That’s straightforward enough: if she would have 10 lollipops left over, then the number of lollipops must be 10 more than the product of 7 and the number of campers.

n = 7c + 10

“…if she eats one of the lollipops herself, she can give each camper 8 lollipops and have none left over”

This is a bit tricky because of her eating one, but the best way to think of that is that the number of lollipops she has is 1 greater than the product of 8 and the number of campers.

n = 8c + 1

Once we have the equations, all we need to do is solve for c. Let’s do that by elimination:

 n = 8c + 1
– (n = 7c + 10)
     0 = c – 9
     9 = c