4×10+5×2/10×5=
40+10/50
50/50
1
4/5+1/5
4×5+5×1/5×5
20+5/25
25/25
[tex] \frac{4}{5} + \frac{2}{10} = \\ \\ \frac{1}{10 \div 2} \\ \\ \ \frac{4 + 1}{5} \\ \\ \frac{5}{5} \\ \\ = \bf 1[/tex]
