Salut! :)
a) b × ( a + c ) = 20 × ( 102 + 203 ) = 20 × 305 = 6100
b) a × c + b × c = c × ( a + b ) = 203 × ( 102 + 20 ) = 203 × 122 = 24766
c) ab + ac = a × ( b + c ) = 102 × ( 20 + 203 ) = 102 × 223 = 22746
d) bc - ab = b × ( c - a ) = 20 × ( 203 - 102 ) = 20 × 101 = 2020