a,18 . 76 + 24 . 18 - 150 = 18 . ( 76 + 24 ) - 150= 18 . 100 - 150 = 1800 - 150=1650
b, 147 + 230 + 53 + 70 = ( 147 + 53 ) + ( 230 + 70) = 200 + 300=500
c, 7 . 85 + 27 . 7 - 7 . 12=(85 + 27 -12 ) . 7=100 . 7=700
Dấu . là phép nhân
1) 18 . 76 + 24 . 18 -150
= 18( 76 + 24 ) - 150
= 18 . 100 -150
= 1800 - 150
= 1650
2) 147+230 +53 + 70
= ( 147 + 53 ) + ( 230 + 70 )
= 200 + 200
= 400
3) 7 × 85 + 27 × 7 - 7 ×12
= 7( 85 + 27 - 12 )
= 7 . 100
= 700