答:2/5X99十2/5
=2/5X(99+1)
=2/5Ⅹ100
=40
50%Ⅹ48十1/2X152
=1/2X48十1/2X152
=1/2x(48十152)
=1/2㐅200
=100
1.25㐅32X0.25
=1.25X8X4✘0.25
=(1.25X8)x(0.25X4)
=10㐅1
=10
1/8x(32十72)
=1/8x32十1/8Ⅹ72
=4十9
=13。
…
=
542÷2–63÷(3＋3×2)–40×3
＝542÷2–63÷(3＋6)–120
＝271–63÷9–120
＝271–7–120
＝264–120
＝144
45×(3＋2)÷5
＝45×5÷5
＝45
