Question

(-9supra10):(18supra25)-(+3supra5):21supra20

Answer 1

Sper sa intelegi cum am facut !! :))

Answer 2

 $(-\frac{\not9^1}{\not{10}_2})\cdot\frac{\not{25}^5}{\not{18}_2}\,-\,\frac{\not3^1}{\not5_1}\cdot\frac{\not{20}^4}{\not{21}_7}=\frac{-5}{4}-\frac{4}{7}=\frac{-35-16}{28}=-\frac{51}{28}$