$\begin{array}{l}A=-25.(75-45)-75.(45-25)\\A=-25.75+25.45-75.45+75.25\\A=(-25.75+75.25)+(25.45-75.45)\\A=75.(-25+25)+45.(25-75)\\A=75.0+45.(-50)\\A=-2250\\\,\\B=(-1).(-1)^2.(-1)^3...(-1)^{100}\\B=(-1)^{1+2+3+\ldots+100}\\B=(-1)^{101.100\div2}\\B=(-1)^{5050}\\B=1\\\,\\C=(-48).72+36.(-304)\\C=-48.2.36+36.(-304)\\C=-96.36+36.(-304)\\C=36.(-96-304)\\C=36.(-400)\\C= -14400\\\,\\D=125.(-61).(-2)^3.(-1)^{2n}\\D=125.(-61).(-8).1\\D=[125.(-8)].(-61)\\D=(-1000).(-61)\\D=61000\end{array}$
