解:
(1)
÷
+
×
,
=
×
+
×
,
=(
+
)×
,
=1×
,
=
;
(2)(
+
-
)×24,
=
×24+
×24-
×24,
=18+12-14,
=30-14,
=16;
(3)
,
=
,
=
÷
,
=
;
(4)
,
=
×(1+0.36+0.64),
=
×2,
=
;
(5)
=12,
×
=12×
,
x=3,
x÷
=3÷
,
x=
;
(6)
x+
x=15,
x=15,
x÷
=15÷
,
x=18;
(7)x×5=100×
,
x×5=75,
x×5÷5=75÷5,
x=15.
分析:(1)把
÷
改寫為
×
,然后再根據(jù)乘法分配律進(jìn)行簡(jiǎn)算;
(2)根據(jù)乘法分配律進(jìn)行簡(jiǎn)算;
(3)先算小括號(hào)里面的減法,再算中括號(hào)里面的除法,最后算括號(hào)外面的除法;
(4)根據(jù)乘法分配律進(jìn)行簡(jiǎn)算;
(5)等式的兩邊同時(shí)乘
,然后等式的兩邊同時(shí)除以
;
(6)先計(jì)算
x+
x=
x,然后等式的兩邊同時(shí)除以
;
(7)先計(jì)算100×
=75,然后等式的兩邊同時(shí)除以5即可.
點(diǎn)評(píng):四則混合運(yùn)算,先弄清運(yùn)算順序,然后再進(jìn)一步計(jì)算即可,能簡(jiǎn)算的要簡(jiǎn)算;解方程,要根據(jù)等式的性質(zhì)進(jìn)行解答.