a, 237 x ( -26 ) + 26 x 137
= ( - 237 ) x ( -1 ) x ( -26 ) + 26 x 137
= ( -237 ) x 26 + 26 x 137
= [ ( -237 ) + 137 ] x 26
= ( -100 ) x 26
= - 2600.
b, 63 x ( -25) + 25 x ( -23)
= ( -63 ) x ( -1 ) x ( -25 ) + 25 x ( -23 )
= ( -63 ) x 25 + 25 x ( -23 )
= 25 x [ ( -63 ) + ( -23 ) ]
= 25 x ( -86)
= - 2150