Răspuns:
Explicație pas cu pas:
207x10= 10x270 = gresit
207x10 = 2070 ; 10x270 = 2700
321x19x0 = 321x0 = 0 = corect
351x6+6x278 = 6x(351-278) = gresit
351x6+6x278 = 6(351+278)
99x520=520x(100-1) = corect
36x1000=360x100 = corect
107x52x3= (52x3)x107= (107x3)52 = corect