x-4=(2x/3)+6+4
Solving equation: x=42 people
2) If Pool A has x tons of water, Pool B will have 400-x tons of water.
x+4=400-x-8
Solve the equation: x= 194 tons.
3) Make the A-type mobile phone 3x, then the B-type mobile phone and the C-type mobile phone are 5x and 9x respectively.
3x+5x+9x=255
Solve the equation: x= 15
Therefore, there are 45, 75 and 135 mobile phones of Type A, Type B and Type C respectively.
4) If X liters of gasoline is pumped from the first tank, the remaining amount of the first tank after pumping is: 120-x liters, and the second tank has gasoline: 45+x liters.
120-x=2(45+x)
Solve the equation, x = 10L.