Answer
10 cm, 17 cm
Work Step by Step
The relationship of two rotating pulleys connected by a belt is:
(diameter of A)(rpm of A) = (diameter of B)(rpm of B).
Now we have
$$
(7+x)\times 80=x\times 136\Longrightarrow 136x-80x=7\times80
\\
\Longrightarrow x=\frac{7\times 80}{136-80}=10\ cm
.$$
Thus, the small pulley is $x=10~cm$ in diameter and the larger pulley is $7+x=7+10=17~cm$ in diameter.
