Let $t$ be TNYWR.

Justin measures the heights of three different trees: a maple, a pine and a spruce. The maple tree is $1 \mathrm{~m}$ taller than the pine tree and the pine tree is $4 \mathrm{~m}$ shorter than the spruce tree. If the ratio of the height of the maple tree to the spruce tree is $t$, what is the height of the spruce tree, in metres? (Write your answer in the form $\frac{a}{b}$, where $a$ and $b$ are positive integers with no common divisor larger than 1.)
Let the height of the spruce tree be $s \mathrm{~m}$.

From the given information, the height of the pine tree is $(s-4) \mathrm{m}$, and so the height of the maple tree is $(s-4) \mathrm{m}+1 \mathrm{~m}=(s-3) \mathrm{m}$.

Thus, the ratio of the height of the maple tree to the height of the spruce tree is $\frac{s-3}{s}=t$.

Simplifying, we obtain $1-\frac{3}{s}=t$ and so $1-t=\frac{3}{s}$ which gives $s=\frac{3}{1-t}$.

Since the answer to (b) is $\frac{25}{64}$, then $s=\frac{3}{1-\frac{25}{64}}=\frac{3}{39 / 64}=\frac{64}{13}$.

ANSWER: $20, \frac{25}{64}, \frac{64}{13}$