Gavin...are the measures to your triangle in cm's If they are...then the formula you should commit to memory...write it on your hand...or something....is area(of a RIGHT ONLY triangle!!) = one-half base times height[in words] but in an equation...a = ½(b × h), If its not a RIGHT TRIANGLE...then its another formula. Those you should commit to memory as well...write them on your pillow(if your mom let's you).
And another question...if your measures aren't in 'cm'...then you should know how to change whatever measures you have...ie...inches...feet...meters...miles...whatever...be able to convert them to cm's.
I'll be glad to help...
J