Question

calculati cat mai rapid: 18×3+18×5=
18×(3+5)=
19×7-19×3=
19×(7-3) =
21×3+21×7+21×10=
45×7-45×3-45×6=​

Answer 1

18x3+18x5=54+90= 144

19x7-19x3=19x(7-3)=19x4= 76

19x(7-3)=19x4= 76

21×3+21×7+21×10=21x(3+7)+210=21x10+210=210+210= 420

45×7-45×3-45×6=​45x(7-3-6)=45x(-2)= -90

Answer 2

18 x 3 + 18 x 5 = 144
18 x (3 + 5) = 144
19 x 7 - 19 x 3 = 76
19 x (7 - 3) = 76
21 x 3 + 21 x 7 + 21 x 10 = 420
45 x 7 - 45 x 3 - 45 x 6 = - 90