25x16x25x84=?

25x16x25x84=25x4x(25x4)x84=100x100x84=84000078+22x7=78+(20+2)x7=78+20x7+2x7=78+140+14=23239x102=39x(100+2)=39x100+39x2=3900+78=3978104x25=(100+4)x25=100x25+4x25=2500+100=2600{25x13}x4==25x13x4=25x4X13...