( 1) 18+8×9
= 18+72
=90 (yuan)
(2)20-9×2
=20- 18
=2 (yuan)
(3) 18×2+8×3
=36+24
=60 (yuan)
definition
Addition: the operation of combining two numbers into one number.
Subtraction: when two addends and one of them are known, the operation of finding the other addend.
Multiplication: the operation of finding the product of two numbers.
Division: the operation of finding another factor by knowing the product of two factors and one of them.