a) 15 x (-2) x (-5) x (-6)
= (15 x (-6) x (-2 x (-5)
= -90 x 10
= -900
b) 4 x 7 x (-11) x (-2)
<=> 4 x 7 x 11 x 2
= 28 x 11 x 2
= 616
a/ 15 x ( - 2 ) x ( - 5 ) x ( - 6 )
= ( - 30 ) x ( - 5 ) x ( - 6 )
= 150 x ( - 6 )
= - 900
b/ 4 x 7 x ( - 11 ) x ( - 2 )
= 28 x ( - 11 ) x ( - 2 )
= ( - 308 ) x ( - 2 )
= 616