解:(1)37.5+20%X=69.5,
37.5+0.2X=69.5,
37.5+0.2X-37.5=69.5-37.5,
0.2X=32,
0.2X÷0.2=32÷0.2,
x=160;
(2)120+
x=168,
120+0.8x=168,
120+0.8x-120=168-120,
0.8x=48,
0.8x÷0.8=48÷0.8,
x=60;
(3)
÷x=
,
÷x×x=
×x,
x=
,
x×
=
×
,
x=
.
分析:(1)原式變?yōu)?7.5+0.2X=69.5,根據(jù)等式的性質(zhì),兩邊同減去37.5,再同除以0.2即可;
(2)原式變?yōu)?20+0.8x=168,根據(jù)等式的性質(zhì),兩邊同減去120,再同除以0.8即可;
(3)根據(jù)等式的性質(zhì),兩邊同乘x,得
x=
,兩邊再同乘
即可.
點評:此題考查了根據(jù)等式的性質(zhì)解方程,即等式兩邊同加、同減、同乘或同除以一個數(shù)(0除外),等式的左右兩邊仍相等;注意“=”上下要對齊.