we know it burns 3/4 of an inch in 1 hour, how about in 4 hours?
3/4 + 3/4 + 3/4 + 3/4, or simply....... [tex]\bf \cfrac{3}{4}\cdot 4\implies 3\cdot \cfrac{4}{4}\implies 3\cdot 1\implies 3[/tex]
so in 4 hours it has burned out 3 inches, it was originally 8 inches, 8 - 3 = 5.
[tex]\bf \begin{array}{cll} \stackrel{x}{hours}&\stackrel{f(x)}{height}\\ \cline{1-2} 0&8\\\\ 1&8-\frac{3}{4}\\\\ 2&8-\frac{3}{4}-\frac{3}{4}\\\\ &8-\frac{3}{4}(2)\\\\ 3&8-\frac{3}{4}-\frac{3}{4}-\frac{3}{4}\\\\ &8-\frac{3}{4}(3)\\\\ x&8-\frac{3}{4}(x) \end{array}~\hspace{10em} f(x)=8-\frac{3}{4}x[/tex]
