The width of a triangle is 6 cm less than its length. if it's perimeter is 80 cm then it's lengths and area are respectively

The length is 14cm the width is 26cm. And according to my calculations, a=l•w so area would be 364.

We can keep this problem with one variable, even though there could potentially be two because of length and width. Since we can't find the width without the length, we'll make L be our variable. Here's what we know so far:
Width=L-6
Length=L
Perimeter=80
How do we find perimeter? We add length + length + width + width, or 2*length + 2*width. Wait! We already know what the length and width are -- we wrote it up there ^ ! So now we just need to set up an equation. 2(length)+2(width)=perimeter, or 2L+2(L-6)=80. Now we just solve! You should get L=23. But wait! We're not done, because while we found length, we still need to know the width. We wrote the formula for width up there ^. It's L-6. Since we know L is 23, 23-6=17.
We're done! 
L=23
W=17.
To check our answer, we do the perimeter formula again. 2(23)+2(17)=80. Is this true? Yes! So we did it right!