a)
[tex]100\% - 10\% = 90\%\\\\50\cdot90\% = 50\cdot0,9 = \underline{45}[/tex]
b)
[tex]100\% + 12\% = 112\%\\\\25\cdot112\% = 25\cdot1,12 = \underline{28}[/tex]
c)
[tex]100\% + 175\% = 275\%\\\\80\cdot275\% = 80\cdot2,75 = \underline{220}[/tex]
d)
[tex]100\% - 100\% = 0\%\\\\1245\cdot 0\% = 1245\cdot0 = \underline{0}[/tex]