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1. 下面各式属于方程的是（
A.$x-3$
B.$x+5=6$
C.$6x＜18$
B
）。A.$x-3$
B.$x+5=6$
C.$6x＜18$
答案
1.B
2.甲数是78，是乙数的3倍，如果设乙数为x，那么下列方程正确的是（
A.$78x=3$
B.$3x=78$
C.$x÷3=78$
B
）。A.$78x=3$
B.$3x=78$
C.$x÷3=78$
答案
2.B
3. 方程$4x+3=15$的解是（
A.$x=1$
B.$x=2$
C.$x=3$
C
）。A.$x=1$
B.$x=2$
C.$x=3$
答案
3.C
4. 根据乘法分配律，$xy+y$可以写成（
A.$(x+y)y$
B.$x+2y$
C.$(x+1)y$
C
）。A.$(x+y)y$
B.$x+2y$
C.$(x+1)y$
答案
4.C
5.一个自然数m，与它相邻的两个自然数是（
A.$2m$和$m÷2$
B.$m+1$和$m-1$
C.$m+2$和$m-2$
B
）。A.$2m$和$m÷2$
B.$m+1$和$m-1$
C.$m+2$和$m-2$
答案
5.B
四、解方程。
$3x-213=45$
$2.8x+3.4x=9.92$
$0.5x+3.6=7.8$
$4.2x-2.4x=12.6$
$7x-3.8×2=8.5$
$23x-3×23=138$
$28-2x=14$
$144÷x=12$
$3x-213=45$
$2.8x+3.4x=9.92$
$0.5x+3.6=7.8$
$4.2x-2.4x=12.6$
$7x-3.8×2=8.5$
$23x-3×23=138$
$28-2x=14$
$144÷x=12$
答案
解：$3x - 213 = 45$
$3x = 45 + 213$
$3x = 258$
$x = 258 ÷ 3$
$x = 86$
解：$2.8x + 3.4x = 9.92$
$6.2x = 9.92$
$x = 9.92 ÷ 6.2$
$x = 1.6$
解：$0.5x + 3.6 = 7.8$
$0.5x = 7.8 - 3.6$
$0.5x = 4.2$
$x = 4.2 ÷ 0.5$
$x = 8.4$
解：$4.2x - 2.4x = 12.6$
$1.8x = 12.6$
$x = 12.6 ÷ 1.8$
$x = 7$
解：$7x - 3.8 × 2 = 8.5$
$7x - 7.6 = 8.5$
$7x = 8.5 + 7.6$
$7x = 16.1$
$x = 16.1 ÷ 7$
$x = 2.3$
解：$23x - 3 × 23 = 138$
$23x - 69 = 138$
$23x = 138 + 69$
$23x = 207$
$x = 207 ÷ 23$
$x = 9$
解：$28 - 2x = 14$
$2x = 28 - 14$
$2x = 14$
$x = 14 ÷ 2$
$x = 7$
解：$144 ÷ x = 12$
$x = 144 ÷ 12$
$x = 12$
$3x = 45 + 213$
$3x = 258$
$x = 258 ÷ 3$
$x = 86$
解：$2.8x + 3.4x = 9.92$
$6.2x = 9.92$
$x = 9.92 ÷ 6.2$
$x = 1.6$
解：$0.5x + 3.6 = 7.8$
$0.5x = 7.8 - 3.6$
$0.5x = 4.2$
$x = 4.2 ÷ 0.5$
$x = 8.4$
解：$4.2x - 2.4x = 12.6$
$1.8x = 12.6$
$x = 12.6 ÷ 1.8$
$x = 7$
解：$7x - 3.8 × 2 = 8.5$
$7x - 7.6 = 8.5$
$7x = 8.5 + 7.6$
$7x = 16.1$
$x = 16.1 ÷ 7$
$x = 2.3$
解：$23x - 3 × 23 = 138$
$23x - 69 = 138$
$23x = 138 + 69$
$23x = 207$
$x = 207 ÷ 23$
$x = 9$
解：$28 - 2x = 14$
$2x = 28 - 14$
$2x = 14$
$x = 14 ÷ 2$
$x = 7$
解：$144 ÷ x = 12$
$x = 144 ÷ 12$
$x = 12$
