\(a,30\cdot6+30\cdot71+20\cdot30\)
=\(30\cdot\left(6+71+20\right)\)
=\(30\cdot97=2910\)
\(b,24\cdot\left(31+119\right)+76\cdot\left(29+121\right)\)
=\(24\cdot150+76\cdot150\)
=\(150\cdot\left(24+76\right)\)
=\(150\cdot100\)
=\(15000\)
\(c,87\cdot23+70\cdot87+43\cdot93\)
=\(87\cdot\left(23+87\right)+43\cdot93\)
=\(87\cdot110+3999\)
=\(9570+3999\)
=13569
a) 15 . 6 . 2 + 3 . 71 . 10 + 20 . 30
= ( 15 . 2 ) . 6 + ( 3 . 10 ) . 71 + 20 . 30
= 30 . 6 + 30 . 71 + 20 . 30
= 30 . ( 6 + 71 + 30 )
= 30 . 107
= 3210
b) 24 . 31 + 24 . 119 + 76 . 29 + 76 . 121
= 24 . ( 31 + 119 ) + 76 . ( 29 + 121 )
= 24 . 150 + 76 . 150
= 150 . ( 24 + 76 )
= 150 . 100
= 15 000
c) 87 . 23 + 43 . 93 + 70 . 87
= 87 . 23 + 70 . 87 + 43 . 93
= 87 . ( 23 + 70 ) + 43 . 93
= 87 . 93 + 43 . 93
= 93 . ( 87 + 43 )
= 93 . 130
= 12 090
a) 15 . 6 . 2 + 3 . 71 . 10 + 20 . 30
= 30 . 6 + 30 . 71 + 30 . 20
= 30 . (6 + 71 + 20) = 30 . 97 = 2910
b) 24 . 31 + 24 . 119 + 76 . 29 + 76 . 121
= 24 . (31 + 119) + 76 . (29 + 121)
= 24 . 150 + 76 . 150 = 150 . (24 + 76)
= 150 . 100
= 15000
c) 87 . 23 + 43 . 93 + 70 . 87
= 43 . 93 + 87 . (23 + 70)
= 43 . 93 + 87 . 93
= 93 . (43 + 87)
= 93 . 130
= 12090
