Ignoring Negative Values?

Hi,

I would like to edit my spreadsheet so it adds up ticket requirements for my rugby club but am having issues with negative values!

Basically when an adult purchases a ticket they are also allocated a free child’s ticket, any extra children are additional purchases, and there is also the option of paying for seats on a coach.

I have put this formula into a cell but it goes wrong when I have a negative value... =(D4-C4)*6+(C4*12)+(E4*5)
1: (D4) Child tickets - (C4) Adult Tickets * £6
2: + (C4) Adult tickets * £12
3: + (E4) Coach seats * £5

The first part is where the negative values are coming from... the formula is taking away the negative value from the total amount to pay and I can’t figure out how to fix it??

Any help is most appreciated.

Thanks