a) 12,48:0,5x6,25x4x2/2x3,12x1,25:0,25x10
= 12,48x2x6,25x4x2/2x3,12x1,25x4x10
= 12,48x2x1,25x6x4x2/(3,12x4)x(1,25x2)x10
= 12,48x(1,25x2)x(6x4x2)/12,48x(1,25x2)x10
= 48/10 = 4,8
b) 38x39-78x19+2010
= 19x2x39-78x19+2010
= 19x78-78x19+2010
= 0+2010 = 2010