解:(1)5x-24×5=151,
5x-120=151,
5x-120+120=151+120,
5x=271,
5x÷5=271÷5,
x=54.2;
(2)
=80%,
=
,
4x=25,
4x÷4=25÷4,
x=
;
(3)14:x=3.5:8,
3.5x=14×8,
3.5x÷3.5=14×8÷3.5,
x=32.
分析:(1)原式變?yōu)?x-120=151,根據(jù)等式的性質(zhì),兩邊同加上120,再同除以5即可;
(2)原式變?yōu)?img class='latex' src='http://thumb.1010pic.com/pic5/latex/6638.png' />=
,根據(jù)比例的基本性質(zhì)改寫為4x=25,再根據(jù)等式的性質(zhì),兩邊同除以4即可;
(3)先根據(jù)比例的基本性質(zhì)改寫為3.5x=14×8,再根據(jù)等式的性質(zhì),兩邊同除以3.5即可.
點(diǎn)評:在解方程時(shí)應(yīng)根據(jù)等式的性質(zhì),即等式兩邊同加上、同減去、同乘上或同除以某一個(gè)數(shù)(0除外),等式的兩邊仍相等,同時(shí)注意“=”上下要對齊.