①8.8+4X=40,
8.8+4X-8.8=40-8.8,
4X÷4=31.2÷4,
X=7.8;
②12X÷3=16,
12X÷3×3=16×3,
12X÷12=48÷12,
X=4;
③6X+2X=56,
8X=56,
8X÷8=56÷8,
X=7;
④3X-0.5X=5,
2.5X=5,
2.5X÷2.5=5÷2.5,
X=2;
⑤0.24X-1.8=4.2,
0.24X-1.8+1.8=4.2+1.8,
0.24X=6,
0.24X÷0.24=6÷0.24,
X=25;
⑥3X+5×0.3=4.5,
3X+1.5=4.5,
3X+1.5-1.5=4.5-1.5,
3X÷3=3÷3,
X=1.
8.8+4x=40
解:4x=40-8.8
4x=31.2
x=31.2/4
x=7.8
8.8+4X=40
4X=40-8.8
4X=31.2
X=31.2除以4
x=7.8
解:4X=40-8.8
4X=31.2
X=7.8
4X=40-8.8
4X=31.2
X=31.2÷4
X=7.8