$$\begin{aligned}(3,75:1,125-0,75):(1,5+0,75)&=(3,75:1,125-0,75):2,25\\&=((3,75 \cdot 1000):(1,125 \cdot 1000) - 0,75):2,25\\&=(3750:1125-0,75):2,25\\&=(3\frac{1}{3}-0,75):2,25\\&=(3\frac{1}{3}-\frac{3}{4}):2,25\\&=(\frac{10}{3}-\frac{3}{4}):2,25\\&=(\frac{40}{12}-\frac{9}{12}):2,25\\&=\frac{31}{12}:2,25=\frac{31}{12}:\frac{225}{100}\\&=(\frac{31}{12}):(\frac{9}{4})=\frac{31}{12} \cdot \frac{4}{9}\\&=(\frac{31}{3})\cdot(\frac{1}{9})=\frac{31}{27}=1\frac{4}{27}\\4\frac{13}{24}+\frac{1}{4}-3\frac{1}{24}&=4\frac{13}{24}+\frac{6}{24}-3\frac{1}{24}\\&=1\frac{18}{24}=1\frac{3}{4}\end{aligned}$$