2. 1，x=50 2，x=36.5 3，2x+ 16 4，x=20×2+ 16。

Three. 1, 3x=4.7-4 3x=0.7 x=7/30 or 0.23 2, -6x=42.9 x=-7. 15.

Four, 1, let's speed at x kilometers per hour 3x+60=300 x=80.

2. Let the lower level have X books 180=2.5x-20 x=80.

3. Set the original X-box Apple15x+165 = 345x =12.

4. Let's assume that the person with X is 5x+15 =100x =17.

5. Let the daughter be x years old and 6(x-3)=33-3 x=8.